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Ultralight aviation

Ultralight aviation (called microlight aviation in some countries) is the flying of lightweight, 1- or 2-seat fixed-wing aircraft. Some countries differentiate between weight-shift control and conventional three-axis control aircraft with ailerons, elevator and rudder, calling the former "microlight" and the latter "ultralight". During the late 1970s and early 1980s, mostly stimulated by the hang gliding movement, many people sought affordable powered flight. As a result, many aviation authorities set up definitions of lightweight, slow-flying aeroplanes that could be subject to minimum regulations. The resulting aeroplanes are commonly called "ultralight aircraft" or "microlights", although the weight and speed limits differ from country to country. In Europe, the sporting (FAI) definition limits the maximum stalling speed to 65 km/h (40 mph) and the maximum take-off weight to 450 kg (992 lb), or 472.5 kg (1,042 lb) if a ballistic parachute is installed. The definition means that the aircraft has a slow landing speed and short landing roll in the event of an engine failure.In most affluent countries, microlights or ultralight aircraft now account for a significant percentage of the global civilian-owned aircraft. For instance in Canada in February 2018, the ultralight aircraft fleet made up to 20.4% of the total civilian aircraft registered. In other countries that do not register ultralight aircraft, like the United States, it is unknown what proportion of the total fleet they make up. In countries where there is no specific extra regulation, ultralights are considered regular aircraft and subject to certification requirements for both aircraft and pilot. Definitions Australia In Australia, ultralight aircraft and their pilots can either be registered with the Hang Gliding Federation of Australia (HGFA) or Recreational Aviation Australia (RA Aus). In all cases, except for privately built single seat ultralight aeroplanes, microlight aircraft or trikes are regulated by the Civil Aviation Regulations. Canada United Kingdom Pilots of a powered, fixed wing aircraft or paramotors do not need a licence, provided its weight with a full fuel tank is not more than 75 kg (165 lb), but they must obey the rules of the air.For heavier microlights the current UK regulations are similar to the European ones, but helicopters and gyroplanes are not included.Other than the very earliest aircraft, all two-seat UK microlights (and until 2007 all single-seaters) have been required to meet an airworthiness standard; BCAR Section S. In 2007, Single Seat DeRegulated (SSDR), a sub-category of single seat aircraft was introduced, allowing owners more freedom for modification and experiments. By 2017 the airworthiness of all single seat microlights became solely the responsibility of the user, but pilots must hold a microlight licence; currently NPPL(M) (National Private Pilots Licence). New Zealand Ultralights in New Zealand are subject to NZCAA General Aviation regulations with microlight specific variations as described in Part 103 and AC103-1. United States The United States FAAs definition of an ultralight is significantly different from that in most other countries and can lead to some confusion when discussing the topic. The governing regulation in the United States is FAR 103 Ultralight Vehicles. In 2004, the FAA introduced the "Light-sport aircraft" category, which resembles some other countries microlight categories. Ultralight aviation is represented by the United States Ultralight Association (USUA), which acts as the US aeroclub representative to the Fédération Aéronautique Internationale. Types There are several categories of aircraft which qualify as ultralights in some countries: Fixed-wing aircraft: traditional airplane-style designs. Weight-shift control trike: use a hang glider-style wing, below which is suspended a three-wheeled carriage which carries the engine and aviators. These aircraft are controlled by pushing against a horizontal control bar in roughly the same way as a hang glider pilot flies. Powered parachute: fuselage-mounted engines with parafoil wings, which are wheeled aircraft. Powered paraglider: backpack engines with parafoil wings, which are foot-launched. Powered hang glider: motorized foot-launched hang glider harness. Autogyro: rotary wing with fuselage-mounted engine, a gyrocopter is different from a helicopter in that the rotating wing is not powered, the engine provides forward thrust and the airflow through the rotary blades causes them to autorotate or "spin up" thereby creating lift. Helicopter: there are a number of single-seat and two-place helicopters which fall under the microlight categories in countries such as New Zealand. However, few helicopter designs fall within the more restrictive ultralight category defined in the United States of America. Hot air balloon: there are numerous ultralight hot air balloons in the US, and several more have been built and flown in France and Australia in recent years. Some ultralight hot air balloons are hopper balloons, while others are regular hot air balloons that carry passengers in a basket. Electric Advancements in batteries, motors, and motor controllers has led to some practical production electric propulsion systems for some ultralight applications. In many ways, ultralights are a good application for electric power as some models are capable of flying with low power, which allows longer duration flights on battery power.In 2007, the first pioneering company in this field, the Electric Aircraft Corporation, began offering engine kits to convert ultralight weight shift trikes to electric power. The 18 hp motor weighs 26 lb (12 kg) and an efficiency of 90% is claimed by designer Randall Fishman. The battery consists of a lithium-polymer battery pack of 5.6kWh which provides 1.5 hours of flying in the trike application. The company claimed a flight recharge cost of 60 cents in 2007.A significant obstacle to the adoption of electric propulsion for ultralights in the U.S. is the weight of the battery, which is considered part of the empty weight of the aircraft despite efforts to have it considered as fuel. As battery energy density improves lighter batteries can be used. See also Aerosport (airshow) Backpack helicopter Jetpack Nanolight Experimental Aircraft Association Recreational Aviation Australia United States Ultralight Association United States Powered Paragliding Association Volksflugzeug References External links Media related to Ultralight aircraft at Wikimedia Commons

Apraxia

Apraxia is a motor disorder caused by damage to the brain (specifically the posterior parietal cortex or corpus callosum), which causes difficulty with motor planning to perform tasks or movements. The nature of the damage determines the disorders severity, and the absence of sensory loss or paralysis helps to explain the level of difficulty. Children may be born with apraxia; its cause is unknown, and symptoms are usually noticed in the early stages of development. Apraxia occurring later in life, known as acquired apraxia, is typically caused by traumatic brain injury, stroke, dementia, Alzheimers disease, brain tumor, or other neurodegenerative disorders. The multiple types of apraxia are categorized by the specific ability and/or body part affected. The term "apraxia" comes from the Greek ἀ- a- ("without") and πρᾶξις praxis ("action"). Types The several types of apraxia include: Apraxia of speech (AOS) is having difficulty planning and coordinating the movements necessary for speech (e.g. potato=totapo, topato). AOS can independently occur without issues in areas such as verbal comprehension, reading comprehension, writing, articulation, or prosody. Buccofacial or orofacial apraxia, the most common type of apraxia, is the inability to carry out facial movements on demand. For example, an inability to lick ones lips, wink, or whistle when requested to do so. This suggests an inability to carry out volitional movements of the tongue, cheeks, lips, pharynx, or larynx on command. Constructional apraxia is the inability to draw, construct, or copy simple configurations, such as intersecting shapes. These patients have difficulty copying a simple diagram or drawing basic shapes. Gait apraxia is the loss of ability to have normal function of the lower limbs such as walking. This is not due to loss of motor or sensory functions. Ideational/conceptual apraxia is having an inability to conceptualize a task and impaired ability to complete multistep actions. This form of apraxia consists of an inability to select and carry out an appropriate motor program. For example, the patient may complete actions in incorrect orders, such as buttering bread before putting it in the toaster, or putting on shoes before putting on socks. Also, a loss occurs in the ability to voluntarily perform a learned task when given the necessary objects or tools. For instance, if given a screwdriver, these patients may try to write with it as if it were a pen, or try to comb their hair with a toothbrush. Ideomotor apraxia is having deficits in the ability to plan or complete motor actions that rely on semantic memory. These patients are able to explain how to perform an action, but unable to "imagine" or act out a movement such as "pretend to brush your teeth" or "pucker as though you bit into a sour lemon." When the ability to perform an action automatically when cued remains intact, though, this is known as automatic-voluntary dissociation. For example, they may not be able to pick up a phone when asked to do so, but can perform the action without thinking when the phone rings. Limb-kinetic apraxia is having the inability to perform precise, voluntary movements of extremities. For example, a person affected by limb apraxia may have difficulty waving hello, tying shoes, or typing on a computer. This type is common in patients who have experienced a stroke, some type of brain trauma, or have Alzheimers disease. Oculomotor apraxia is having difficulty moving the eye on command, especially with saccade movements that direct the gaze to targets. This is one of the three major components of Balints syndrome. Causes Apraxia is most often due to a lesion located in the dominant (usually left) hemisphere of the brain, typically in the frontal and parietal lobes. Lesions may be due to stroke, acquired brain injuries, or neurodegenerative diseases such as Alzheimers disease or other dementias, Parkinsons disease, or Huntingtons disease. Also, apraxia possibly may be caused by lesions in other areas of the brain.Ideomotor apraxia is typically due to a decrease in blood flow to the dominant hemisphere of the brain and particularly the parietal and premotor areas. It is frequently seen in patients with corticobasal degeneration.Ideational apraxia has been observed in patients with lesions in the dominant hemisphere near areas associated with aphasia, but more research is needed on ideational apraxia due to brain lesions. The localization of lesions in areas of the frontal and temporal lobes would provide explanation for the difficulty in motor planning seen in ideational apraxia, as well as its difficulty to distinguish it from certain aphasias.Constructional apraxia is often caused by lesions of the inferior nondominant parietal lobe, and can be caused by brain injury, illness, tumor, or other condition that can result in a brain lesion. Diagnosis Although qualitative and quantitative studies exist, little consensus exists on the proper method to assess for apraxia. The criticisms of past methods include failure to meet standard psychometric properties and research-specific designs that translate poorly to nonresearch use.The Test to Measure Upper Limb Apraxia (TULIA) is one method of determining upper limb apraxia through the qualitative and quantitative assessment of gesture production. In contrast to previous publications on apraxic assessment, the reliability and validity of TULIA was thoroughly investigated. The TULIA consists of subtests for the imitation and pantomime of nonsymbolic ("put your index finger on top of your nose"), intransitive ("wave goodbye"), and transitive ("show me how to use a hammer") gestures. Discrimination (differentiating between well- and poorly performed tasks) and recognition (indicating which object corresponds to a pantomimed gesture) tasks are also often tested for a full apraxia evaluation.However, a strong correlation may not be seen between formal test results and actual performance in everyday functioning or activities of daily living (ADLs). A comprehensive assessment of apraxia should include formal testing, standardized measurements of ADLs, observation of daily routines, self-report questionnaires, and targeted interviews with the patients and their relatives.As stated above, apraxia should not be confused with aphasia (the inability to understand language); however, they frequently occur together. Apraxia is so often accompanied by aphasia that many believe that if a person displays AOS, then the patient also having some level of aphasia should be assumed. Treatment Treatment for individuals with apraxia includes speech therapy, occupational therapy, and physical therapy. Currently, no medications are indicated for the treatment of apraxia, only therapy treatments. Generally, treatments for apraxia have received little attention for several reasons, including the tendency for the condition to resolve spontaneously in acute cases. Additionally, the very nature of the automatic-voluntary dissociation of motor abilities that defines apraxia means that patients may still be able to automatically perform activities if cued to do so in daily life. Nevertheless, patients experiencing apraxia have less functional independence in their daily lives, and that evidence for the treatment of apraxia is scarce. However, a literature review of apraxia treatment to date reveals that although the field is in its early stages of treatment design, certain aspects can be included to treat apraxia.One method is through rehabilitative treatment, which has been found to positively impact apraxia, as well as ADLs. In this review, rehabilitative treatment consisted of 12 different contextual cues, which were used to teach patients how to produce the same gesture under different contextual situations. Additional studies have also recommended varying forms of gesture therapy, whereby the patient is instructed to make gestures (either using objects or symbolically meaningful and nonmeaningful gestures) with progressively less cuing from the therapist. Patients with apraxia may need to use a form of alternative and augmentative communication depending on the severity of the disorder. In addition to using gestures as mentioned, patients can also use communication boards or more sophisticated electronic devices if needed.No single type of therapy or approach has been proven as the best way to treat a patient with apraxia, since each patients case varies. One-on-one sessions usually work the best, though, with the support of family members and friends. Since everyone responds to therapy differently, some patients will make significant improvements, while others will make less progress. The overall goal for treatment of apraxia is to treat the motor plans for speech, not treating at the phoneme (sound) level. Individuals with apraxia of speech should receive treatment that focuses on the repetition of target words and rate of speech. The overall goal for treatment of apraxia should be to improve speech intelligibility, rate of speech, and articulation of targeted words. Prognosis The prognosis for individuals with apraxia varies. With therapy, some patients improve significantly, while others may show very little improvement. Some individuals with apraxia may benefit from the use of a communication aid. However, many people with apraxia are no longer able to be independent. Those with limb-kinetic and/or gait apraxia should avoid activities in which they might injure themselves or others.Occupational therapy, physical therapy, and play therapy may be considered as other references to support patients with apraxia. These treatments could work along with the SLP to provide the best therapy for people with apraxia. Because people with limb apraxia may have trouble directing their motor movements, however, occupational therapy for stroke or other brain injury can be difficult. See also Praxis (process) Ataxia Aging movement control Developmental coordination disorder Lists of language disorders References Further reading External links Acquired Apraxia of Speech: A Treatment Overview Apraxia: Symptoms, Causes, Tests, Treatments ApraxiaKids GettingTheWordOutOnApraxia.com: A Community for Parents of Children with Apraxia

4

4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures. In mathematics Four is the smallest composite number, its proper divisors being 1 and 2. Four is the sum and product of two with itself: 2 {\displaystyle 2} + 2 {\displaystyle 2} = 4 {\displaystyle 4} = 2 {\displaystyle 2} x 2 {\displaystyle 2} , the only number b {\displaystyle b} such that a {\displaystyle a} + a {\displaystyle a} = b {\displaystyle b} = a {\displaystyle a} x a {\displaystyle a} , which also makes four the smallest squared prime number p 2 {\displaystyle p^{2}} . In Knuths up-arrow notation, 2 ↑↑ 2 = 2 ↑↑↑ 2 = 4, and so forth, for any number of up arrows. By consequence, four is the only square one more than a prime number, specifically three. The sum of the first four prime numbers two + three + five + seven is the only sum of four consecutive prime numbers that yields an odd prime number, seventeen, which is the fourth super-prime. Four lies between the first proper pair of twin primes, three and five, which are the first two Fermat primes, like seventeen, which is the third. On the other hand, the square of four 42, equivalently the fourth power of two 24, is sixteen; the only number that has a b {\displaystyle a^{b}} = b a {\displaystyle b^{a}} as a form of factorization. Holistically, there are four elementary arithmetic operations in mathematics: addition (+), subtraction (−), multiplication (×), and division (÷); and four basic number systems, the real numbers R {\displaystyle \mathbb {R} } , rational numbers Q {\displaystyle \mathbb {Q} } , integers Z {\displaystyle \mathbb {Z} } , and natural numbers N {\displaystyle \mathbb {N} } . Each natural number divisible by 4 is a difference of squares of two natural numbers, i.e. 4 x {\displaystyle 4x} = y 2 {\displaystyle y^{2}} − z 2 {\displaystyle z^{2}} . A number is a multiple of 4 if its last two digits are a multiple of 4. For example, 1092 is a multiple of 4 because 92 = 4 × 23. Lagranges four-square theorem states that every positive integer can be written as the sum of at most four square numbers. Three are not always sufficient; 7 for instance cannot be written as the sum of three squares.There are four all-Harshad numbers: 1, 2, 4, and 6. 12, which is divisible by four thrice over, is a Harshad number in all bases except octal. A four-sided plane figure is a quadrilateral or quadrangle, sometimes also called a tetragon. It can be further classified as a rectangle or oblong, kite, rhombus, and square. Four is the highest degree general polynomial equation for which there is a solution in radicals.The four-color theorem states that a planar graph (or, equivalently, a flat map of two-dimensional regions such as countries) can be colored using four colors, so that adjacent vertices (or regions) are always different colors. Three colors are not, in general, sufficient to guarantee this. The largest planar complete graph has four vertices.A solid figure with four faces as well as four vertices is a tetrahedron, which is the smallest possible number of faces and vertices a polyhedron can have. The regular tetrahedron, also called a 3-simplex, is the simplest Platonic solid. It has four regular triangles as faces that are themselves at dual positions with the vertices of another tetrahedron. Tetrahedra can be inscribed inside all other four Platonic solids, and tessellate space alongside the regular octahedron in the alternated cubic honeycomb. Four-dimensional space is the highest-dimensional space featuring more than three regular convex figures: Two-dimensional: infinitely many regular polygons. Three-dimensional: five regular polyhedra; the five Platonic solids which are the tetrahedron, cube, octahedron, dodecahedron, and icosahedron. Four-dimensional: six regular polychora; the 5-cell, 8-cell or tesseract, 16-cell, 24-cell, 120-cell, and 600-cell. The 24-cell, made of regular octahedra, has no analogue in any other dimension; it is self-dual, with its 24-cell honeycomb dual to the 16-cell honeycomb. Five-dimensional and every higher dimension: three regular convex n {\displaystyle n} -polytopes, all within the infinite family of regular n {\displaystyle n} -simplexes, n {\displaystyle n} -hypercubes, and n {\displaystyle n} -orthoplexes.The fourth dimension is also the highest dimension where regular self-intersecting figures exist: Two-dimensional: infinitaly many regular star polygons. Three-dimensional: four regular star polyhedra, the regular Kepler-Poinsot star polyhedra. Four-dimensional: ten regular star polychora, the Schläfli–Hess star polychora. They contain cells of Kepler-Poinsot polyhedra alongside regular tetrahedra, icosahedra and dodecahedra. Five-dimensional and every higher dimension: zero regular star-polytopes; uniform star polytopes in dimensions n {\displaystyle n} > 4 {\displaystyle 4} are the most symmetric, which mainly originate from stellations of regular n {\displaystyle n} -polytopes.Altogether, sixteen (or 16 = 42) regular convex and star polychora are generated from symmetries of four (4) Coxeter Weyl groups and point groups in the fourth dimension: the A 4 {\displaystyle \mathrm {A} _{4}} simplex, B 4 {\displaystyle \mathrm {B} _{4}} hypercube, F 4 {\displaystyle \mathrm {F} _{4}} icositetrachoric, and H 4 {\displaystyle \mathrm {H} _{4}} hexacosichoric groups; with the D 4 {\displaystyle \mathrm {D} _{4}} demihypercube group generating two alternative constructions. There are also sixty-four (or 64 = 43) four-dimensional Bravais lattices, and sixty-four uniform polychora in the fourth dimension based on the same A 4 {\displaystyle \mathrm {A} _{4}} , B 4 {\displaystyle \mathrm {B} _{4}} , F 4 {\displaystyle \mathrm {F} _{4}} and H 4 {\displaystyle \mathrm {H} _{4}} Coxeter groups, and extending to prismatic groups of uniform polyhedra, including one special non-Wythoffian form, the grand antiprism. There are also two infinite families of duoprisms and antiprismatic prisms in the fourth dimension. Four-dimensional differential manifolds have some unique properties. There is only one differential structure on R n {\displaystyle \mathbb {R} ^{n}} except when n {\displaystyle n} = 4 {\displaystyle 4} , in which case there are uncountably many. The smallest non-cyclic group has four elements; it is the Klein four-group. An alternating groups are not simple for values n {\displaystyle n} ≤ 4 {\displaystyle 4} . Further extensions of the real numbers under Hurwitzs theorem states that there are four normed division algebras: the real numbers R {\displaystyle \mathbb {R} } , the complex numbers C {\displaystyle \mathbb {C} } , the quaternions H {\displaystyle \mathbb {H} } , and the octonions O {\displaystyle \mathbb {O} } . Under Cayley–Dickson constructions, the sedenions S {\displaystyle \mathbb {S} } constitute a further fourth extension over R {\displaystyle \mathbb {R} } . The real numbers are ordered, commutative and associative algebras, as well as alternative algebras with power-associativity. The complex numbers C {\displaystyle \mathbb {C} } share all four multiplicative algebraic properties of the reals R {\displaystyle \mathbb {R} } , without being ordered. The quaternions loose a further commutative algebraic property, while holding associative, alternative, and power-associative properties. The octonions are alternative and power-associative, while the sedenions are only power-associative. The sedenions and all further extensions of these four normed division algebras are solely power-associative with non-trivial zero divisors, which makes them non-division algebras. R {\displaystyle \mathbb {R} } has a vector space of dimension 1, while C {\displaystyle \mathbb {C} } , H {\displaystyle \mathbb {H} } , O {\displaystyle \mathbb {O} } and S {\displaystyle \mathbb {S} } work in algebraic number fields of dimensions 2, 4, 8, and 16, respectively. List of basic calculations Evolution of the Hindu-Arabic digit Brahmic numerals represented 1, 2, and 3 with as many lines. 4 was simplified by joining its four lines into a cross that looks like the modern plus sign. The Shunga would add a horizontal line on top of the digit, and the Kshatrapa and Pallava evolved the digit to a point where the speed of writing was a secondary concern. The Arabs 4 still had the early concept of the cross, but for the sake of efficiency, was made in one stroke by connecting the "western" end to the "northern" end; the "eastern" end was finished off with a curve. The Europeans dropped the finishing curve and gradually made the digit less cursive, ending up with a digit very close to the original Brahmin cross.While the shape of the character for the digit 4 has an ascender in most modern typefaces, in typefaces with text figures the glyph usually has a descender, as, for example, in. On the seven-segment displays of pocket calculators and digital watches, as well as certain optical character recognition fonts, 4 is seen with an open top.Television stations that operate on channel 4 have occasionally made use of another variation of the "open 4", with the open portion being on the side, rather than the top. This version resembles the Canadian Aboriginal syllabics letter ᔦ. The magnetic ink character recognition "CMC-7" font also uses this variety of "4". In religion Buddhism Four Noble Truths – Dukkha, Samudaya, Nirodha, Magga Four sights – observations which affected Prince Siddhartha deeply and made him realize the sufferings of all beings, and compelled him to begin his spiritual journey—an old man, a sick man, a dead man, and an ascetic Four Great Elements – earth, water, fire, and wind Four Heavenly Kings Four Foundations of Mindfulness – contemplation of the body, contemplation of feelings, contemplation of mind, contemplation of mental objects Four Right Exertions Four Bases of Power Four jhānas Four arūpajhānas Four Divine Abidings – loving-kindness, compassion, sympathetic joy, and equanimity Four stages of enlightenment – stream-enterer, once-returner, non-returner, and arahant Four main pilgrimage sites – Lumbini, Bodh Gaya, Sarnath, and Kusinara Judeo-Christian symbolism The Tetragrammaton is the four-letter name of God. Ezekiel has a vision of four living creatures: a man, a lion, an ox, and an eagle. The four Matriarchs (foremothers) of Judaism are Sarah, Rebekah, Leah, and Rachel. The Four Species (lulav, hadass, aravah and etrog) are taken as one of the mitzvot on the Jewish holiday of Sukkot. (Judaism) The Four Cups of Wine to drink on the Jewish holiday of Passover. (Judaism) The Four Questions to be asked on the Jewish holiday of Passover. (Judaism) The Four Sons to be dealt with on the Jewish holiday of Passover. (Judaism) The Four Expressions of Redemption to be said on the Jewish holiday of Passover. (Judaism) The four Gospels: Matthew, Mark, Luke, and John. (Christianity) The Four Horsemen of the Apocalypse ride in the Book of Revelation. (Christianity) The four holy cities of Judaism: Jerusalem, Hebron, Safed, and Tiberius Hinduism There are four Vedas: Rigveda, Samaveda, Yajurveda and Atharvaveda. In Puruṣārtha, there are four aims of human life: Dharma, Artha, Kāma, Moksha. The four stages of life Brahmacharya (student life), Grihastha (household life), Vanaprastha (retired life) and Sannyasa (renunciation). The four primary castes or strata of society: Brahmana (priest/teacher), Kshatriya (warrior/politician), Vaishya (landowner/entrepreneur) and Shudra (servant/manual laborer). The swastika symbol is traditionally used in Hindu religions as a sign of good luck and signifies good from all four directions. The god Brahma has four faces. There are four yugas: Satya, Dvapara, Treta and Kali Islam Eid al-Adha lasts for four days, from the 10th to the 14th of Dhul Hijja. The four holy cities of Islam: Mecca, Medina, Jerusalem and Damascus. The four tombs in the Green Dome: Muhammad, Abu Bakr, Umar ibn Khattab and Isa ibn Maryam (Jesus). There are four Rashidun or Rightly Guided Caliphs: Abu Bakr, Umar ibn al-Khattab, Uthman ibn Affan and Ali ibn Abi Talib. The Four Arch Angels in Islam are: Jibraeel (Gabriel), Mikaeel (Michael), Izraeel (Azrael), and Israfil (Raphael) There are four months in which war is not permitted: Muharram, Rajab, Dhu al-Qidah and Dhu al-Hijjah. There are four Sunni schools of fiqh: Hanafi, Shafi`i, Maliki and Hanbali. There are four major Sunni Imams: Abū Ḥanīfa, Muhammad ibn Idris ash-Shafi`i, Malik ibn Anas and Ahmad ibn Hanbal. There are four books in Islam: Taurait, Zaboor, Injeel, Quran. Waiting for four months is ordained for those who take an oath for abstention from their wives. The waiting period of the woman whose husband dies is four months and ten days. When Abraham said: "My Lord, show me how You give life to the dead," Allah said: "Why! Do you have no faith?" Abraham replied: "Yes, but in order that my heart be at rest." He said: "Then take four birds, and tame them to yourself, then put a part of them on every hill, and summon them; they will come to you flying. [Al-Baqara 2:260] The respite of four months was granted to give time to the mushriks in Surah At-Tawba so that they should consider their position carefully and decide whether to make preparation for war or to emigrate from the country or to accept Islam. Those who accuse honorable women (of unchastity) but do not produce four witnesses, flog them with eighty lashes, and do not admit their testimony ever after. They are indeed transgressors. [An-Noor 24:4] Taoism Four Symbols of I Ching Other In a more general sense, numerous mythological and cosmogonical systems consider Four corners of the world as essentially corresponding to the four points of the compass. Four is the sacred number of the Zia, an indigenous tribe located in the U.S. state of New Mexico. The Chinese, the Koreans, and the Japanese are superstitious about the number four because it is a homonym for "death" in their languages. In Slavic mythology, the god Svetovid has four heads. In politics Four Freedoms: four fundamental freedoms that Franklin D. Roosevelt declared ought to be enjoyed by everyone in the world: Freedom of Speech, Freedom of Religion, Freedom from Want, Freedom from Fear. Gang of Four: Popular name for four Chinese Communist Party leaders who rose to prominence during Chinas Cultural Revolution, but were ousted in 1976 following the death of Chairman Mao Zedong. Among the four was Maos widow, Jiang Qing. Since then, many other political factions headed by four people have been called "Gangs of Four". In computing Four bits (half a byte) are sometimes called a nibble. In science A tetramer is an oligomer formed out of four sub-units. In astronomy Four terrestrial (or rocky) planets in the Solar System: Mercury, Venus, Earth, and Mars. Four giant gas/ice planets in the Solar System: Jupiter, Saturn, Uranus, and Neptune. Four of Jupiters moons (the Galilean moons) are readily visible from Earth with a hobby telescope. Messier object M4, a magnitude 7.5 globular cluster in the constellation Scorpius. The Roman numeral IV stands for subgiant in the Yerkes spectral classification scheme. In biology Four is the number of nucleobase types in DNA and RNA – adenine, guanine, cytosine, thymine (uracil in RNA). Many chordates have four feet, legs or leglike appendages (tetrapods). The mammalian heart consists of four chambers. Many mammals (Carnivora, Ungulata) use four fingers for movement. All insects with wings except flies and some others have four wings. Insects of the superorder Endopterygota, also known as Holometabola, such as butterflies, ants, bees, beetles, fleas, flies, moths, and wasps, undergo holometabolism—complete metamorphism in four stages—from (1) embryo (ovum, egg), to (2) larva (such as grub, caterpillar), then (3) pupa (such as the chrysalis), and finally (4) the imago. In the common ABO blood group system, there are four blood types (A, B, O, AB). Humans have four canines and four wisdom teeth. The cows stomach is divided in four digestive compartments: reticulum, rumen, omasum and abomasum. In chemistry Valency of carbon (that is basis of life on the Earth) is four. Also because of its tetrahedral crystal bond structure, diamond (one of the natural allotropes of carbon) is the hardest known naturally occurring material. It is also the valence of silicon, whose compounds form the majority of the mass of the Earths crust. The atomic number of beryllium There are four basic states of matter: solid, liquid, gas, and plasma. In physics Special relativity and general relativity treat nature as four-dimensional: 3D regular space and one-dimensional time are treated together and called spacetime. Also, any event E has a light cone composed of four zones of possible communication and cause and effect (outside the light cone is strictly incommunicado). There are four fundamental forces (electromagnetism, gravitation, the weak nuclear force, and the strong nuclear force). In statistical mechanics, the four functions inequality is an inequality for four functions on a finite distributive lattice. In logic and philosophy The symbolic meanings of the number four are linked to those of the cross and the square. "Almost from prehistoric times, the number four was employed to signify what was solid, what could be touched and felt. Its relationship to the cross (four points) made it an outstanding symbol of wholeness and universality, a symbol which drew all to itself". Where lines of latitude and longitude intersect, they divide the earth into four proportions. Throughout the world kings and chieftains have been called "lord of the four suns" or "lord of the four quarters of the earth", which is understood to refer to the extent of their powers both territorially and in terms of total control of their subjects doings. The Square of Opposition, in both its Aristotelian version and its Boolean version, consists of four forms: A ("All S is R"), I ("Some S is R"), E ("No S is R"), and O ("Some S is not R"). In regard to whether two given propositions can have the same truth value, there are four separate logical possibilities: the propositions are subalterns (possibly both are true, and possibly both are false); subcontraries (both may be true, but not that both are false); contraries (both may be false, but not that both are true); or contradictories (it is not possible that both are true, and it is not possible that both are false). Aristotle held that there are basically four causes in nature: the material, the formal, the efficient, and the final. The Stoics held with four basic categories, all viewed as bodies (substantial and insubstantial): (1) substance in the sense of substrate, primary formless matter; (2) quality, matters organization to differentiate and individualize something, and coming down to a physical ingredient such as pneuma, breath; (3) somehow holding (or disposed), as in a posture, state, shape, size, action, and (4) somehow holding (or disposed) toward something, as in relative location, familial relation, and so forth. Immanuel Kant expounded a table of judgments involving four three-way alternatives, in regard to (1) Quantity, (2) Quality, (3) Relation, (4) Modality, and, based thereupon, a table of four categories, named by the terms just listed, and each with three subcategories. Arthur Schopenhauers doctoral thesis was On the Fourfold Root of the Principle of Sufficient Reason. Franz Brentano held that any major philosophical period has four phases: (1) Creative and rapidly progressing with scientific interest and results; then declining through the remaining phases, (2) practical, (3) increasingly skeptical, and (4) literary, mystical, and scientifically worthless—until philosophy is renewed through a new periods first phase. (See Brentanos essay "The Four Phases of Philosophy and Its Current State" 1895, tr. by Mezei and Smith 1998.) C. S. Peirce, usually a trichotomist, discussed four methods for overcoming troublesome uncertainties and achieving secure beliefs: (1) the method of tenacity (policy of sticking to initial belief), (2) the method of authority, (3) the method of congruity (following a fashionable paradigm), and (4) the fallibilistic, self-correcting method of science (see "The Fixation of Belief", 1877); and four barriers to inquiry, barriers refused by the fallibilist: (1) assertion of absolute certainty; (2) maintaining that something is unknowable; (3) maintaining that something is inexplicable because absolutely basic or ultimate; (4) holding that perfect exactitude is possible, especially such as to quite preclude unusual and anomalous phenomena (see "F.R.L." [First Rule of Logic], 1899). Paul Weiss built a system involving four modes of being: Actualities (substances in the sense of substantial, spatiotemporally finite beings), Ideality or Possibility (pure normative form), Existence (the dynamic field), and God (unity). (See Weisss Modes of Being, 1958). Karl Popper outlined a tetradic schema to describe the growth of theories and, via generalization, also the emergence of new behaviors and living organisms: (1) problem, (2) tentative theory, (3) (attempted) error-elimination (especially by way of critical discussion), and (4) new problem(s). (See Poppers Objective Knowledge, 1972, revised 1979.) John Boyd (military strategist) made his key concept the decision cycle or OODA loop, consisting of four stages: (1) observation (data intake through the senses), (2) orientation (analysis and synthesis of data), (3) decision, and (4) action. Boyd held that his decision cycle has philosophical generality, though for strateg

4

ists the point remains that, through swift decisions, one can disrupt an opponents decision cycle. Richard McKeon outlined four classes (each with four subclasses) of modes of philosophical inquiry: (1) Modes of Being (Being); (2) Modes of Thought (That which is); (3) Modes of Fact (Existence); (4) Modes of Simplicity (Experience)—and, corresponding to them, four classes (each with four subclasses) of philosophical semantics: Principles, Methods, Interpretations, and Selections. (See McKeons "Philosophic Semantics and Philosophic Inquiry" in Freedom and History and Other Essays, 1989.) Jonathan Lowe (E.J. Lowe) argues in The Four-Category Ontology, 2006, for four categories: kinds (substantial universals), attributes (relational universals and property-universals), objects (substantial particulars), and modes (relational particulars and property-particulars, also known as "tropes"). (See Lowes "Recent Advances in Metaphysics," 2001, Eprint) Four opposed camps of the morality and nature of evil: moral absolutism, amoralism, moral relativism, and moral universalism. In technology The resin identification code used in recycling to identify low-density polyethylene. Most furniture has four legs – tables, chairs, etc. The four color process (CMYK) is used for printing. Wide use of rectangles (with four angles and four sides) because they have effective form and capability for close adjacency to each other (houses, rooms, tables, bricks, sheets of paper, screens, film frames). In the Rich Text Format specification, language code 4 is for the Chinese language. Codes for regional variants of Chinese are congruent to 4 mod 256. Credit card machines have four-twelve function keys. On most phones, the 4 key is associated with the letters G, H, and I, but on the BlackBerry Pearl, it is the key for D and F. On many computer keyboards, the "4" key may also be used to type the dollar sign ($) if the shift key is held down. It is the number of bits in a nibble, equivalent to half a byte In internet slang, "4" can replace the word "for" (as "four" and "for" are pronounced similarly). For example, typing "4u" instead of "for you". In Leetspeak, "4" may be used to replace the letter "A". The TCP/IP stack consists of four layers. In transport Many internal combustion engines are called four-stroke engines because they complete one thermodynamic cycle in four distinct steps: Intake, compression, power, and exhaust. Most vehicles, including motor vehicles, and particularly cars/automobiles and light commercial vehicles have four road wheels. "Quattro", meaning four in the Italian language, is used by Audi as a trademark to indicate that all-wheel drive (AWD) technologies are used on Audi-branded cars. The word "Quattro" was initially used by Audi in 1980 in its original 4WD coupé, the Audi Quattro. Audi also has a privately held subsidiary company called quattro GmbH. List of highways numbered 4 In sports In the Australian Football League, the top level of Australian rules football, each team is allowed 4 "interchanges" (substitute players), who can be freely substituted at any time, subject to a limit on the total number of substitutions. In baseball: There are four bases in the game: first base, second base, third base, and home plate; to score a run, an offensive player must complete, in the sequence shown, a circuit of those four bases. When a batter receives four pitches that the umpire declares to be "balls" in a single at-bat, a base on balls, informally known as a "walk", is awarded, with the batter sent to first base. For scoring, number 4 is assigned to the second baseman. Four is the most runs that can be scored on any single at bat, whereby all three baserunners and the batter score (the most common being via a grand slam). The fourth batter in the batting lineup is called the cleanup hitter. In basketball, the number four is used to designate the power forward position, often referred to as "the four spot" or "the four". In cricket, a four is a specific type of scoring event, whereby the ball crosses the boundary after touching the ground at least one time, scoring four runs. Taking four wickets in four consecutive balls is typically referred to as a double hat trick (two consecutive, overlapping hat tricks). In American Football teams get four downs to reach the line of gain. In rowing, a four refers to a boat for four rowers, with or without coxswain. In rowing nomenclature, 4− represents a coxless four and 4+ represents a coxed four. In rugby league: A try is worth 4 points. One of the two starting centres wears the jersey number 4. (An exception to this rule is the Super League, which uses static squad numbering.) In rugby union: One of the two starting locks wears the jersey number 4. In the standard bonus points system, a point is awarded in the league standings to a team that scores at least 4 tries in a match, regardless of the match result. In other fields The phrase "four-letter word" is used to describe many swear words in the English language. Four is the only number whose name in English has the same number of letters as its value. Four (四, formal writing: 肆, pinyin sì) is considered an unlucky number in Chinese, Korean, Vietnamese and Japanese cultures mostly in Eastern Asia because it sounds like the word "death" (死, pinyin sǐ). To avoid complaints from people with tetraphobia, many numbered product lines skip the "four": e.g. Nokia cell phones (there was no series beginning with a 4 until the Nokia 4.2), Palm PDAs, etc. Some buildings skip floor 4 or replace the number with the letter "F", particularly in heavily Asian areas. See tetraphobia and Numbers in Chinese culture. In Pythagorean numerology (a pseudocience) the number 4 represents security and stability. The number of characters in a canonical four-character idiom. In the NATO phonetic alphabet, the digit 4 is called "fower". In astrology, Cancer is the 4th astrological sign of the Zodiac. In Tarot, The Emperor is the fourth trump or Major Arcana card. In Tetris, a game named for the Greek word for 4, every shape in the game is formed of 4 blocks each. 4 represents the number of Justices on the Supreme Court of the United States necessary to grant a writ of certiorari (i.e., agree to hear a case; it is one less than the number necessary to render a majority decision) at the courts current size. Number Four is a character in the book series Lorien Legacies. In the performing arts, the fourth wall is an imaginary barrier which separates the audience from the performers, and is "broken" when performers communicate directly to the audience. In music In written music, common time is constructed of four beats per measure and a quarter note receives one beat. In popular or modern music, the most common time signature is also founded on four beats, i.e., 4/4 having four quarter note beats. The common major scale is built on two sets of four notes (e.g., CDEF, GABC), where the first and last notes create an octave interval (a pair-of-four relationship). The interval of a perfect fourth is a foundational element of many genres of music, represented in music theory as the tonic and subdominant relationship. Four is also embodied within the circle of fifths (also known as circle of fourths), which reveals the interval of four in more active harmonic contexts. The typical number of movements in a symphony. The number of completed, numbered symphonies by Johannes Brahms. The number of strings on a violin, a viola, a cello, double bass, a cuatro, a typical bass guitar, and a ukulele, and the number of string pairs on a mandolin. "Four calling birds" is the gift on the fourth day of Christmas in the carol "The Twelve Days of Christmas". Groups of four Big Four (disambiguation) Four basic operations of arithmetic: addition, subtraction, multiplication, division. Greek classical elements (fire, air, water, earth). Four seasons: spring, summer, autumn, winter. The Four Seasons (disambiguation) A leap year generally occurs every four years. Approximately four weeks (4 times 7 days) to a lunar month (synodic month = 29.53 days). Thus the number four is universally an integral part of primitive sacred calendars. Four weeks of Advent (and four Advent candles on the Advent wreath). Four cardinal directions: north, south, east, west. Four Temperaments: sanguine, choleric, melancholic, phlegmatic. Four Humors: blood, yellow bile, black bile, phlegm. Four Great Ancient Capitals of China. Four-corner method. Four Asian Tigers, referring to the economies of Hong Kong, Taiwan, South Korea, and Singapore Cardinal principles. Four cardinal virtues: justice, prudence, temperance, fortitude. Four suits of playing cards: hearts, diamonds, clubs, spades. Four nations of the United Kingdom: England, Wales, Scotland, Northern Ireland. Four provinces of Ireland: Munster, Ulster, Leinster, Connacht. Four estates: politics, administration, judiciary, journalism. Especially in the expression "Fourth Estate", which means journalism. Four Corners is the only location in the United States where four states come together at a single point: Colorado, Utah, New Mexico, and Arizona. Four Evangelists – Matthew, Mark, Luke, and John Four Doctors of Western Church – Saint Gregory the Great, Saint Ambrose, Saint Augustine, and Saint Jerome Four Doctors of Eastern Church – Saint John Chrysostom, Saint Basil the Great, and Gregory of Nazianzus and Saint Athanasius Four Galilean moons of Jupiter – Io, Europa, Ganymede, and Callisto The Gang of Four was a Chinese communist political faction. The Fantastic Four: Mr. Fantastic, The Invisible Woman, The Human Torch, The Thing. The Teenage Mutant Ninja Turtles: Leonardo, Michelangelo, Donatello, Raphael The Beatles were also known as the "Fab Four": John Lennon, Paul McCartney, George Harrison, Ringo Starr. Gang of Four is a British post-punk rock band formed in the late 1970s. Four rivers in the Garden of Eden (Genesis 2:10–14): Pishon (perhaps the Jaxartes or Syr Darya), Gihon (perhaps the Oxus or Amu Darya), Hiddekel (Tigris), and Prat (Euphrates). There are also four years in a single Olympiad (duration between the Olympic Games). Many major international sports competitions follow this cycle, among them the FIFA World Cup and its womens version, the FIBA World Championships for men and women, and the Rugby World Cup. There are four limbs on the human body. Four Houses of Hogwarts in the Harry Potter series: Gryffindor, Hufflepuff, Ravenclaw, Slytherin. Four known continents of the world in the A Song of Ice and Fire series: Westeros, Essos, Sothoryos, Ulthos. Each Grand Prix in Nintendos Mario Kart series is divided into four cups and each cup is divided into four courses. The Mushroom Cup, Flower Cup, Star Cup, and Special Cup make up the Nitro Grand Prix, while the Shell Cup, Banana Cup, Leaf Cup, and the Lightning Cup make up the Retro Grand Prix. See also List of highways numbered 4 References Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group. (1987): 55–58 External links Marijn.Org on Why is everything four? A few thoughts on the number four, by Penelope Merritt at samuel-beckett.net The Number 4 The Positive Integer 4 Prime curiosities: 4

Intractability

Intractable may refer to: Intractable conflict, a form of complex, severe, and enduring conflict Intractable pain, pain which cannot be controlled/cured by any known treatment Intractability (complexity), in computational complexity theory

Ear pain

Ear pain, also known as earache or otalgia, is pain in the ear. Primary ear pain is pain that originates from the ear. Secondary ear pain is a type of referred pain, meaning that the source of the pain differs from the location where the pain is felt. Most causes of ear pain are non-life-threatening. Primary ear pain is more common than secondary ear pain, and it is often due to infection or injury. The conditions that cause secondary (referred) ear pain are broad and range from temporomandibular joint syndrome to inflammation of the throat.In general, the reason for ear pain can be discovered by taking a thorough history of all symptoms and performing a physical examination, without need for imaging tools like a CT scan. However, further testing may be needed if red flags are present like hearing loss, dizziness, ringing in the ear or unexpected weight loss.Management of ear pain depends on the cause. If there is a bacterial infection, antibiotics are sometimes recommended and over the counter pain medications can help control discomfort. Some causes of ear pain require a procedure or surgery.83 percent of children have at least one episode of a middle ear infection by three years of age. Signs and symptoms Ear pain can present in one or both ears. It may or may not be accompanied by other symptoms such as fever, sensation of the world spinning, ear itchiness, or a sense of fullness in the ear. The pain may or may not worsen with chewing. The pain may also be continuous or intermittent.Ear pain due to an infection is the most common in children and can occur in babies. Adults may need further evaluation if they have hearing loss, dizziness or ringing in the ear. Additional red flags include diabetes, a weakened immune system, swelling seen on the outer ear, or swelling along the jaw. Causes Ear pain has a variety of causes, the majority of which are not life-threatening. Ear pain can originate from a part of the ear itself, known as primary ear pain, or from an anatomic structure outside the ear that is perceived as pain within the ear, known as secondary ear pain. Secondary ear pain is a type of referred pain, meaning that the source of the pain differs from the location where the pain is felt. Primary ear pain is more common in children, whereas secondary (referred) pain is more common in adults.Primary ear pain is most commonly caused by infection or injury to one of the parts of the ear. External ear Many conditions involving the external ear will be visible to the naked eye. Because the external ear is the most exposed portion of the ear, it is vulnerable to trauma or environmental exposures. Blunt trauma, such as a blow to the ear, can result in a hematoma, or collection of blood between the cartilage and perichondrium of the ear. This type of injury is particularly common in contact sports such as wrestling and boxing. Environmental injuries include sunburn, frostbite, or contact dermatitis.Less common causes of external ear pain include: Auricular Cellulitis: a superficial infection of the ear that may be precipitated by trauma, an insect bite, or ear piercing Perichondritis: infection of the perichondrium, or fascia surrounding the ear cartilage, which can develop as a complication of untreated auricular cellulitis. It is important to identify and treat perichondritis with antibiotics to avoid permanent ear deformities. Relapsing polychondritis: a systemic inflammatory condition involving cartilage in many parts of the body, but often including the cartilage of both ears. The severity and prognosis of the disease varies widely. Otitis externa Otitis externa, also known as "swimmers ear", is a cellulitis of the external ear canal. In North America, 98% of cases are caused by bacteria, and the most common causative organisms are Pseudomonas and Staph aureus. Risk factors include exposure to excessive moisture (e.g. from swimming or a warm climate) and disruption of the protective cerumen barrier, which can result from aggressive ear cleaning or placing objects in the ear.Malignant otitis externa is a rare and potentially life-threatening complication of otitis externa in which the infection spreads from the ear canal into the surrounding skull base, hence becoming an osteomyelitis. It occurs largely in diabetic patients. It is very rare in children, though can be seen in immunocompromised children and adults. Pseudomonas is the most common causative organism. The pain tends to be more severe than in uncomplicated otitis externa, and laboratory studies often reveal elevated inflammatory markers (ESR and/or CRP). The infection may extend to cranial nerves, or rarely to the meninges or brain. Examination of the ear canal may reveal granulation tissue in the inferior canal. It is treated with several weeks of IV and oral antibiotics, usually fluoroquinolones. Mechanical obstruction Earwax impaction: results in 12 million medical visits annually in the United States. Cerumen impaction may cause ear pain, but it can also prevent thorough examination of the ear and identification of an alternate source of pain. Foreign body: commonly include insects or small objects like beads Less common Herpes zoster: varicella zoster virus can reactivate in an area that includes the ear. Reactivation can produce pain and visible vesicles within the ear canal and, when combined with facial paralysis due to facial nerve involvement, is called Ramsay Hunt syndrome. Tumors: the most common ear canal tumor is squamous cell carcinoma. Symptoms can resemble those of otitis externa, and cancer should be considered if the symptoms are not improving on appropriate treatment. Middle and inner ear Acute otitis media Acute otitis media is an infection of the middle ear. More than 80% of children experience at least one episode of otitis media by age 3 years. Acute otitis media is also most common in these first 3 years of life, though older children may also experience it. The most common causative bacteria are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Otitis media often occurs with or following cold symptoms. The diagnosis is made by the combination of symptoms and examination of the tympanic membrane for redness, bulging, and/or a middle ear effusion (collection of fluid within the middle ear).Complications of otitis media include hearing loss, facial nerve paralysis, or extension of infection to surrounding anatomic structures, including: Mastoiditis: infection of the air cells in the mastoid process, the area of the skull located right behind the ear Petrositis: infection of the petrous portion of the temporal bone Labyrinthitis Meningitis Subdural abscess Brain abscess Cerebral venous sinus thrombosis Trauma Barotrauma: results from changes in atmospheric pressure that occur when descending in a plane or deep diving. As atmospheric pressure increases with descent, the eustachian tube collapses due to pressure within the middle ear being less than the external pressure, which causes pain. In severe cases, middle ear hemorrhage or tympanic membrane rupture can result. Tympanic membrane rupture: disruption of the eardrum. This can be caused by a blow to the ear, blast injury, barotrauma, or direct penetration of the tympanic membrane by an object entering the ear. Referred ear pain A variety of conditions can cause irritation of one of the nerves that provides sensation to the ear. Conditions causing irritation the trigeminal nerve (cranial nerve V): Temporomandibular joint syndrome: inflammation or abnormal movements of the joint between the jaw and skull. These disorders are most common in women of childbearing age, and are uncommon in children younger than 10 years old. Myofascial pain syndrome: pain in the muscles involved in chewing. There may be certain parts of the muscles or tendons (connective tissue connecting the muscles to bones) that are especially painful when pressed Trigeminal neuralgia: attacks of shooting pain down the face that may be triggered by touching the face or temperature changes Dental pain from cavities or an abscess Oral cavity carcinomaConditions causing irritation of the facial nerve (cranial nerve VII) or glossopharyngeal nerve (cranial nerve IX): Tonsillitis: infection/inflammation of the tonsils Post-tonsillectomy: pain following surgical removal of the tonsils Pharyngitis: infection/inflammation of the throat Sinusitis Parotitis: inflammation of the parotid gland, the salivary gland right in front of the ear Carcinoma of the oropharynx (base of tongue, soft palate, pharyngeal wall, tonsils)Conditions causing irritation of the vagus nerve (cranial nerve X): GERD Myocardial ischemia (inadequate oxygen supply to the heart muscle)Conditions causing irritation of cervical nerves C2-C3: Cervical spine trauma, arthritis (joint inflammation), or tumor Temporal arteritis: an autoimmune disorder leading to inflammation of the temporal artery, a large artery in the head. This condition tends to occur in adults older than 50. Pathophysiology Primary ear pain The ear can be anatomically divided into the external ear, the external auditory canal, the middle ear, and the inner ear. These three are indistinguishable in terms of the pain experienced. Secondary ear pain Many different nerves provide sensation to the various parts of the ear, including cranial nerves V (trigeminal), VII (facial), IX (glossopharyngeal), and X (vagus), and the great auricular nerve (cervical nerves C2-C3). These nerves also supply other parts of the body, from the mouth to the chest and abdomen. Irritation of these nerves in another part of the body has the potential to produce pain in the ear. This is called referred pain. Irritation of the trigeminal nerve (cranial nerve V) is the most common cause of referred ear pain. Diagnostic While some disorders may require specific imaging or testing, most etiologies of ear pain are diagnosed clinically. Because the differential for ear pain is so broad, there is no consensus on the best diagnostic framework to use. One approach is to differentiate by time course, as primary causes of ear pain are typically more acute in nature, while secondary causes of ear pain are more chronic. Acute causes may be further distinguished by the presence of fever (indicating an underlying infection) or the absence of fever (suggesting a structural problem, such as such as trauma or other injury to the ear). Etiologies leading to chronic pain may be broken down by the presence or absence of worrisome clinical features, also known as red flags. One red flag is the presence of one or multiple risk factors including smoking, heavy alcohol use (greater than 3.5 drinks per day), diabetes, coronary artery disease, and older age (greater than 50). These factors increase the risk of having a serious cause of ear pain, like cancer or a serious infection. In particular, second hand smoke may increase risk of acute otitis media in children. In addition, swimming is the most significant risk factor for otitis externae, though other risk factors include high humidity in the ear canal, eczema and/or ear trauma.If red flags are present it may be necessary to do additional workup such as a CT scan or biopsy to rule out a more dangerous diagnosis. Such diagnoses include malignant (or necrotizing) otitis externa, mastoiditis, temporal arteritis, and cancer. It is important to note that while the presence of a red flag does raise suspicion for one of these four disease, it does not guarantee a diagnosis as any one symptom can be seen in a variety of situations. For example, jaw claudication can be seen in temporal arteritis, but also in TMJ dysfunction.If there are no red flags, other sources of referred ear pain become more likely and are reasonable to pursue. *Indicates a "Cant Miss" diagnosis or a red flag. Management Management of ear pain depends on the underlying cause. Antibiotics While not all causes of ear pain are treated with antibiotics, those caused by bacterial infections of the ear are usually treated with antibiotics known to cover the common bacterial organisms for that type of infection. Many bacterial ear infections are treated with cleaning of the area, topical or systemic antibiotics, and oral analgesics for comfort. Some types of bacterial ear infections can benefit from warm compresses included in the treatment. Some of the causes of ear pain that are typically treated with either a topical or systemic antibiotic include: Uncomplicated acute bacterial otitis externa (AOE). For symptoms that are not responsive to treatment within 10 days, a physician should evaluate for necrotizing external otitis. Acute otitis media (AOM) self-resolves within 24–48 hours in 80% of cases. If it does not self-resolve, AOM thought to be caused by bacteria is treated with systemic antibiotics. If symptoms do not respond to a week of treatment, a physician should evaluate for mastoiditis. Acute folliculitis. Auricular cellulitis. Suppurative otitis media. There is also a risk for tympanic membrane rupture. Perichondritis. An otorhinolaryngologist should also evaluate it and if a foreign body is present in the cartilage, this foreign body should be removed. If there is cartilage involvement, then more advance care with hospitalization is needed. Sinusitis can cause secondary ear pain. Treating the underlying sinusitis will treat the ear pain. (See sinusitis.)Some bacterial infections may require a more advanced treatment with evaluation by otorhinolaryngology, IV antibiotics, and hospital admission. Necrotizing external otitis is potentially fatal and should be evaluated by an otorhinolaryngologist with admission to the hospital and IV antibiotics.(See otitis externa.) Acute mastoiditis is treated with admission to the hospital, otorhinolaryngology consultation and empiric IV antibiotics. Cases with intracranial involvement are treated with a mastoidectomy with myringotomy. Chondritis. Procedures Some causes of ear pain require procedural management alone, by a health professional, or in addition to antibiotic therapy. Keratosis obturans is treated with removal of impacted desquamated keratin debris in the ear canal. Chronic perichondritis and chondritis that continues to be symptomatic despite appropriate antibiotic management may require surgical debridement. Surgical drainage could be required. Bullous myringitis leads to the development of bullae on the tympanic membrane that can be punctured to give pain relief. Foreign body in the ear canal can cause pain and be treated with careful removal. Infected sebaceous cyst is treated with incision and drainage of the cysts, oral antibiotics and otorhinolaryngology assessment. Other Given the variety of causes of ear pain, some causes require treatment other than antibiotics and procedures. Relapsing polychondritis is an autoimmune disease treated with immunomodulating medications (medications that help modulate the immune system). Temporomandibular joint dysfunction can lead to secondary ear pain and can be initially treated with a soft food diet, NSAIDs, application of a heat pack, massage of local area, and a referral to a dentist. Myofascial pain syndromes are initially treated with NSAIDs and physical therapy. Local anesthetic injection into the muscle trigger point can be considered in severe cases. Glossopharyngeal neuralgia is treated with carbamazepine. Epidemiology 2/3 of people presenting with ear pain were diagnosed with some sort of primary otalgia and 1/3 were diagnosed with some sort secondary otalgia.A common cause of primary otalgia is ear infection called otitis media, meaning an infection behind the eardrum. The peak age for children to get acute otitis media is ages 6–24 months. One review paper wrote that 83% of children had at least one episode of acute otitis media by 3 years of age. Worldwide, there are 709 millions cases of acute otitis media every year. Hearing loss globally due to ear infection is estimated to be 30 people in every 10,000. Around the world there is around 21,000 to 28,000 deaths due to complications from ear infections. These complications include brain abscesses and meningitis. Otitis externae peaks at age 7–12 years of age and around 10% of people has had it at least once in their lives.Cerumen impaction occurs in 1 out of every 10 children, 1 in every 20 adults and 1 in every 3 elderly citizens.Barotrauma occurs around 1 in every 1000 people.Of people presenting with ear pain, only 3% was diagnosed with eustachian tube dysfunction. History Not much was known about ear pain and acute otitis media before the 17th century. It was a common phenomenon with no treatment. That changed when the otoscope was invented in the 1840s by Anton von Troeltsh in Germany. Another shift came with the invention of antibiotics. Before antibiotics was introduced there use to be a high rate of ear infections spreading to the bone around the ear, but that is now considered a rare complication. Society and culture There was previously a strong tradition of treating acute otitis media with amoxicillin. One quote from the 1980s shows this sentiment by saying "any child with an earache has an acute amoxicillin deficiency". However, people started realizing that using antibiotics too much can cause bacteria to gain resistance. Increasing resistance makes antibiotics less effective. The term antibiotic stewardship is then used to describe the systematic effort to educate antibiotic prescribers to only give these medications when they are warranted. In particular to children, most ear pain resolves by itself with no complications. There are guidelines in place to help determine when antibiotics for ear pain are needed in children. The ear itself played a role in treatment via acupuncture, also known as auriculotherapy. It was believed that acupuncture of the ear could be used to correct other pain or disorders in the body. Such practices may have started as far back as the Stone Age. The first documentation of auriculotherapy in Europe was in the 1600s. One physician described stimulating the ear by burning or scarring to treat sciatic pain, while another physician applied this treatment for toothache. Paul Nogier is known as the father of ear acupuncture for his theory that parts of the ear corresponds to other areas of the body in a reliable fashion. Research There are currently studies going on delivering antibiotics directly into the middle ear. References == External links ==

Central retinal vein occlusion

Central retinal vein occlusion, also CRVO, is when the central retinal vein becomes occluded, usually through thrombosis. The central retinal vein is the venous equivalent of the central retinal artery and both may become occluded. Since the central retinal artery and vein are the sole source of blood supply and drainage for the retina, such occlusion can lead to severe damage to the retina and blindness, due to ischemia (restriction in blood supply) and edema (swelling).CRVO can cause ocular ischemic syndrome. Nonischemic CRVO is the milder form of the disease. It may progress to the more severe ischemic type. CRVO can also cause glaucoma. Diagnosis Despite the role of thrombosis in the development of CRVO, a systematic review found no increased prevalence of thrombophilia (an inherent propensity to thrombosis) in patients with retinal vascular occlusion. Treatment Treatment consists of Anti-VEGF drugs like Lucentis or intravitreal steroid implant (Ozurdex) and Pan-Retinal Laser Photocoagulation usually. Underlying conditions also require treatment. CRVO without ischemia has better visual prognosis than ischemic CRVO. A systematic review studied the effectiveness of the anti-VEGF drugs ranibizumab and pagatanib sodium for patients with non-ischemic CRVO. Though there was a limited sample size, participants in both treatment groups showed improved visual acuity over 6 month periods, with no safety concerns. See also Central retinal artery occlusion Branch retinal artery occlusion Branch retinal vein occlusionEylea Iridodialysis Ischemic optic neuropathy References == External links ==

Denasalization

In phonetics, denasalization is the loss of nasal airflow in a nasal sound, such as a nasal consonant or a nasal vowel. That may be due to speech pathology but also occurs when the sinuses are blocked from a common cold, when it is called a nasal voice, which is not a linguistic term. Acoustically, it is the "absence of the expected nasal resonance." The symbol in the Extended IPA is ⟨◌͊⟩. When one speaks with a cold, the nasal passages still function as a resonant cavity so a denasalized nasal [m͊] does not sound like a voiced oral stop [b], and a denasalized vowel [a͊] does not sound like an oral vowel [a]. However, there are cases of historical or allophonic denasalization that have produced oral stops. In some languages with nasal vowels, such as Paicĩ, nasal consonants may occur only before nasal vowels; before oral vowels, prenasalized stops are found. That allophonic variation is likely to be from a historical process of partial denasalization. Similarly, several languages around Puget Sound underwent a process of denasalization about 100 years ago. Except in special speech registers, such as baby talk, the nasals [m, n] became the voiced stops [b, d]. It appears from historical records that there was an intermediate stage in which the stops were prenasalized stops [ᵐb, ⁿd] or poststopped nasals [mᵇ, nᵈ]. Something similar has occurred with word-initial nasals in Korean; in some contexts, /m/, /n/ are denasalized to [b, d]. The process is sometimes represented with the IPA [m͊] and [n͊], which simply places the IPA ◌͊ denasalization diacritic on [m] and [n] to show the underlying phoneme.In speech pathology, practice varies in whether ⟨m͊⟩ is a partially denasalized /m/, with ⟨b⟩ for full denasalization, or is a target /m/ whether partially denasalized or a fully denasalized [b]. See also Nasalization Hypernasal speech == References ==

Stress

Stress may refer to: Science and medicine Stress (biology), an organisms response to a stressor such as an environmental condition Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase or sentence Stress (mechanics), the internal forces that neighboring particles of a continuous material exert on each other Occupational stress, stress related to ones job Psychological stress, a feeling of strain and pressure Surgical stress, systemic response to surgical injury Arts, entertainment, and media Music Groups and musicians Stress (Brazilian band), a Brazilian heavy metal band Stress (British band), a British rock band Stress (pop rock band), an early 1980s melodic rock band from San Diego Stress (musician) (born 1977), hip hop singer from Switzerland Stress (record producer) (born 1979), artistic name of Can Canatan, Swedish musician and record producer Albums Stress (Anonymus album), 1997 Stress (Daddy Freddy album), 1991 Stress (Stress album), self-titled album by Brazilian band Stress Stress: The Extinction Agenda, 1994 album by Organized Konfusion Songs "Stress" (Justice song), 2007 song by Justice "Stress" (Odd Børre song), 1968 song by Odd Børre "Stress", a song by Godsmack from Godsmack "Stress", a 2000 song by Jims Big Ego "The Stress", a 1989 song by Chisato Moritaka Other music Stress (music), a type of emphasis placed on a particular note or set of notes Other arts, entertainment, and media Stress (card game), a card game Stress (journal), a medical journal "Stress" (The Unit), an episode of the television series The Unit Other uses Stress (font), varying stroke widths of a font See also All pages with titles containing Stress Emphasis (disambiguation) Stress cracking (disambiguation) Stress intensity (disambiguation) Stress tensor (disambiguation) Stress test (disambiguation) Tension (disambiguation)

Acute infectious thyroiditis

Acute infectious thyroiditis (AIT) also known as suppurative thyroiditis, microbial inflammatory thyroiditis, pyrogenic thyroiditis and bacterial thyroiditis.The thyroid is normally very resistant to infection. Due to a relatively high amount of iodine in the tissue, as well as high vascularity and lymphatic drainage to the region, it is difficult for pathogens to infect the thyroid tissue. Despite all this, a persistent fistula from the piriform sinus may make the left lobe of the thyroid susceptible to infection and abscess formation. AIT is most often caused by a bacterial infection but can also be caused by a fungal or parasitic infection, most commonly in an immunocompromised host. Signs and symptoms In most cases AIT is characterized by onset of pain, firmness, tenderness, redness or swelling in the anterior aspect of the neck. Patients will also present with a sudden fever, difficulty swallowing and difficulty controlling the voice. Symptoms may be present from 1 to 180 days, with most symptoms lasting an average of about 18 days. The main issue associated with the diagnosis of AIT is differentiating it from other more commonly seen forms of thyroid conditions. Pain, fever and swelling are often much more severe and continue to get worse in people who have AIT compared to those with other thyroid conditions. Causes Despite the thyroid gland being extremely resistant to infection, it is still susceptible to infection by various bacteria. The cause can be almost any bacterium. Staphylococcus aureus, Streptococcus pyogenes, Staphylococcus epidermidis, and Streptococcus pneumoniae in descending order are the organisms most commonly isolated from acute thyroiditis cases in children. Other aerobic organisms are Klebsiella sp, Haemophilus influenza, Streptococcus viridans, Eikenella corrodens, Enterobacteriaceae, and salmonella sp. Occurrences of AIT are most common in patients with prior thyroid disease such as Hashimotos thyroiditis or thyroid cancer. The most common cause of infection in children is a congenital abnormality such as pyriform sinus fistula. In most cases, the infection originates in the piriform sinus and spreads to the thyroid via the fistula. In many reported cases of AIT the infection occurs following an upper respiratory tract infection. One study found that of the reported cases of AIT, 66% occurred after an acute illness involving the upper respiratory tract. Although the rates of infection are still very low, cases of AIT have been on the rise in recent years due to the higher occurrence of immune-compromised patients. Other causes of AIT are commonly due to contamination from an outside source and are included below. Repeated fine needle aspirates Perforation of esophagus Regional infection Diagnosis Patients who are suspected of having AIT often undergo tests to detect for elevated levels of white blood cells as well as an ultrasound to reveal unilobular swelling. Depending on the age and immune status of the patient more invasive procedures may be performed such as fine needle aspiration of the neck mass to facilitate a diagnosis. In cases where the infection is thought to be associated with a sinus fistula it is often necessary to confirm the presence of the fistula through surgery or laryngoscopic examination. While invasive procedures can often tell definitively whether or not a fistula is present, new studies are working on the use of computed tomography as a useful method to visualize and detect the presence of a sinus fistula. Diagnostic tests Fever, redness, swelling Pain Blood tests of thyroid functions including TSH, T4 and T3 are usually normal Ultrasonographic examination often shows the abscess or swelling in thyroid Gallium scan will be positive Barium swallow will show fistula connection to the piriform sinus and left lobe Elevated white blood cell count Elevated erythrocyte sedimentation rate Fine-needle aspiration Subtypes of thyroiditis Treatment Treatment of AIT involves antibiotic treatment. Based on the offending organism found on microscopic examination of the stained fine needle aspirate, the appropriate antibiotic treatment is determined. In the case of a severe infection, systemic antibiotics are necessary. Empirical broad spectrum antimicrobial treatment provides preliminary coverage for a variety of bacteria, including S. aureus and S. pyogenes. Antimicrobial options include penicillinase-resistant penicillins (ex: cloxacillin, dicloxacillin) or a combination of a penicillin and a beta-lactamase inhibitor. However, in patients with a penicillin allergy, clindamycin or a macrolide can be prescribed. The majority of anaerobic organisms involved with AIT are susceptible to penicillin. Certain Gram-negative bacilli (ex: Prevotella, Fusobacteriota, and Porphyromonas) are exhibiting an increased resistance based on the production of beta-lactamase. Patients who have undergone recent penicillin therapy have demonstrated an increase in beta-lactamase-producing (anaerobic and aerobic) bacteria. Clindamycin, or a combination of metronidazole and a macrolide, or a penicillin combined with a beta-lactamase inhibitor is recommended in these cases. Fungal thyroiditis can be treated with amphotericin B and fluconazole. Early treatment of AIT prevents further complications. However, if antibiotic treatment does not manage the infection, surgical drainage is required. Symptoms or indications requiring drainage include continued fever, high white blood cell count, and continuing signs of localized inflammation. The draining procedure is also based on clinical examination or ultrasound/CT scan results that indicate an abscess or gas formation. Another treatment of AIT involves surgically removing the fistula. This treatment is often the option recommended for children. However, in cases of an antibiotic resistant infection or necrotic tissue, a lobectomy is recommended. If diagnosis and/or treatment is delayed, the disease could prove fatal. Epidemiology Acute infectious thyroiditis is very rare, with it only accounting for about 0.1–0.7% of all thyroiditis. Large hospitals tend to only see two cases of AIT annually. For the few cases of AIT that are seen the statistics seem to show a pattern. AIT is found in children and young adults between the ages of 20 and 40. The occurrence of the disease in people between 20 and 40 is only about 8% with the other 92% being in children. Men and women are each just as likely to get the disease. If left untreated, there is a 12% mortality rate. References == External links ==

Influenza

Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin from one to four days after exposure to the virus (typically two days) and last for about 2–8 days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia, which can be caused by the virus or by a subsequent bacterial infection. Other complications of infection include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease. There are four types of influenza virus, termed influenza viruses A, B, C, and D. Aquatic birds are the primary source of Influenza A virus (IAV), which is also widespread in various mammals, including humans and pigs. Influenza B virus (IBV) and Influenza C virus (ICV) primarily infect humans, and Influenza D virus (IDV) is found in cattle and pigs. IAV and IBV circulate in humans and cause seasonal epidemics, and ICV causes a mild infection, primarily in children. IDV can infect humans but is not known to cause illness. In humans, influenza viruses are primarily transmitted through respiratory droplets produced from coughing and sneezing. Transmission through aerosols and intermediate objects and surfaces contaminated by the virus also occur. Frequent hand washing and covering ones mouth and nose when coughing and sneezing reduce transmission. Annual vaccination can help to provide protection against influenza. Influenza viruses, particularly IAV, evolve quickly, so flu vaccines are updated regularly to match which influenza strains are in circulation. Vaccines currently in use provide protection against IAV subtypes H1N1 and H3N2 and one or two IBV subtypes. Influenza infection is diagnosed with laboratory methods such as antibody or antigen tests and a polymerase chain reaction (PCR) to identify viral nucleic acid. The disease can be treated with supportive measures and, in severe cases, with antiviral drugs such as oseltamivir. In healthy individuals, influenza is typically self-limiting and rarely fatal, but it can be deadly in high-risk groups. In a typical year, 5–15% of the population contracts influenza. There are 3–5 million severe cases annually, with up to 650,000 respiratory-related deaths globally each year. Deaths most commonly occur in high-risk groups, including young children, the elderly, and people with chronic health conditions. In temperate regions of the world, the number of influenza cases peaks during winter, whereas in the tropics influenza can occur year-round. Since the late 1800s, large outbreaks of novel influenza strains that spread globally, called pandemics, have occurred every 10–50 years. Five flu pandemics have occurred since 1900: the Spanish flu in 1918–1920, which was the most severe flu pandemic, the Asian flu in 1957, the Hong Kong flu in 1968, the Russian flu in 1977, and the swine flu pandemic in 2009. Signs and symptoms The time between exposure to the virus and development of symptoms, called the incubation period, is 1–4 days, most commonly 1–2 days. Many infections, however, are asymptomatic. The onset of symptoms is sudden, and initial symptoms are predominately non-specific, including fever, chills, headaches, muscle pain or aching, a feeling of discomfort, loss of appetite, lack of energy/fatigue, and confusion. These symptoms are usually accompanied by respiratory symptoms such as a dry cough, sore or dry throat, hoarse voice, and a stuffy or runny nose. Coughing is the most common symptom. Gastrointestinal symptoms may also occur, including nausea, vomiting, diarrhea, and gastroenteritis, especially in children. The standard influenza symptoms typically last for 2–8 days. A 2021 study suggests influenza can cause long lasting symptoms in a similar way to long COVID.Symptomatic infections are usually mild and limited to the upper respiratory tract, but progression to pneumonia is relatively common. Pneumonia may be caused by the primary viral infection or by a secondary bacterial infection. Primary pneumonia is characterized by rapid progression of fever, cough, labored breathing, and low oxygen levels that cause bluish skin. It is especially common among those who have an underlying cardiovascular disease such as rheumatic heart disease. Secondary pneumonia typically has a period of improvement in symptoms for 1–3 weeks followed by recurrent fever, sputum production, and fluid buildup in the lungs, but can also occur just a few days after influenza symptoms appear. About a third of primary pneumonia cases are followed by secondary pneumonia, which is most frequently caused by the bacteria Streptococcus pneumoniae and Staphylococcus aureus. Virology Types of virus Influenza viruses comprise four species. Each of the four species is the sole member of its own genus, and the four influenza genera comprise four of the seven genera in the family Orthomyxoviridae. They are: Influenza A virus (IAV), genus Alphainfluenzavirus Influenza B virus (IBV), genus Betainfluenzavirus Influenza C virus (ICV), genus Gammainfluenzavirus Influenza D virus (IDV), genus DeltainfluenzavirusIAV is responsible for most cases of severe illness as well as seasonal epidemics and occasional pandemics. It infects people of all ages but tends to disproportionately cause severe illness in the elderly, the very young, and those who have chronic health issues. Birds are the primary reservoir of IAV, especially aquatic birds such as ducks, geese, shorebirds, and gulls, but the virus also circulates among mammals, including pigs, horses, and marine mammals. IAV is classified into subtypes based on the viral proteins haemagglutinin (H) and neuraminidase (N). As of 2019, 18 H subtypes and 11 N subtypes have been identified. Most potential combinations have been reported in birds, but H17-18 and N10-11 have only been found in bats. Only H subtypes H1-3 and N subtypes N1-2 are known to have circulated in humans, the current IAV subtypes in circulation being H1N1 and H3N2. IAVs can be classified more specifically to also include natural host species, geographical origin, year of isolation, and strain number, such as H1N1/A/duck/Alberta/35/76.IBV mainly infects humans but has been identified in seals, horses, dogs, and pigs. IBV does not have subtypes like IAV but has two antigenically distinct lineages, termed the B/Victoria/2/1987-like and B/Yamagata/16/1988-like lineages, or simply (B/)Victoria(-like) and (B/)Yamagata(-like). Both lineages are in circulation in humans, disproportionately affecting children. IBVs contribute to seasonal epidemics alongside IAVs but have never been associated with a pandemic.ICV, like IBV, is primarily found in humans, though it also has been detected in pigs, feral dogs, dromedary camels, cattle, and dogs. ICV infection primarily affects children and is usually asymptomatic or has mild cold-like symptoms, though more severe symptoms such as gastroenteritis and pneumonia can occur. Unlike IAV and IBV, ICV has not been a major focus of research pertaining to antiviral drugs, vaccines, and other measures against influenza. ICV is subclassified into six genetic/antigenic lineages.IDV has been isolated from pigs and cattle, the latter being the natural reservoir. Infection has also been observed in humans, horses, dromedary camels, and small ruminants such as goats and sheep. IDV is distantly related to ICV. While cattle workers have occasionally tested positive to prior IDV infection, it is not known to cause disease in humans. ICV and IDV experience a slower rate of antigenic evolution than IAV and IBV. Because of this antigenic stability, relatively few novel lineages emerge. Genome and structure Influenza viruses have a negative-sense, single-stranded RNA genome that is segmented. The negative sense of the genome means it can be used as a template to synthesize messenger RNA (mRNA). IAV and IBV have eight genome segments that encode 10 major proteins. ICV and IDV have seven genome segments that encode nine major proteins. Three segments encode three subunits of an RNA-dependent RNA polymerase (RdRp) complex: PB1, a transcriptase, PB2, which recognizes 5 caps, and PA (P3 for ICV and IDV), an endonuclease. The matrix protein (M1) and membrane protein (M2) share a segment, as do the non-structural protein (NS1) and the nuclear export protein (NEP). For IAV and IBV, hemagglutinin (HA) and neuraminidase (NA) are encoded on one segment each, whereas ICV and IDV encode a hemagglutinin-esterase fusion (HEF) protein on one segment that merges the functions of HA and NA. The final genome segment encodes the viral nucleoprotein (NP). Influenza viruses also encode various accessory proteins, such as PB1-F2 and PA-X, that are expressed through alternative open reading frames and which are important in host defense suppression, virulence, and pathogenicity.The virus particle, called a virion, is pleomorphic and varies between being filamentous, bacilliform, or spherical in shape. Clinical isolates tend to be pleomorphic, whereas strains adapted to laboratory growth typically produce spherical virions. Filamentous virions are about 250 nanometers (nm) by 80 nm, bacilliform 120–250 by 95 nm, and spherical 120 nm in diameter. The virion consists of each segment of the genome bound to nucleoproteins in separate ribonucleoprotein (RNP) complexes for each segment, all of which are surrounded by a lipid bilayer membrane called the viral envelope. There is a copy of the RdRp, all subunits included, bound to each RNP. The envelope is reinforced structurally by matrix proteins on the interior that enclose the RNPs, and the envelope contains HA and NA (or HEF) proteins extending outward from the exterior surface of the envelope. HA and HEF proteins have a distinct "head" and "stalk" structure. M2 proteins form proton ion channels through the viral envelope that are required for viral entry and exit. IBVs contain a surface protein named NB that is anchored in the envelope, but its function is unknown. Life cycle The viral life cycle begins by binding to a target cell. Binding is mediated by the viral HA proteins on the surface of the evelope, which bind to cells that contain sialic acid receptors on the surface of the cell membrane. For N1 subtypes with the "G147R" mutation and N2 subtypes, the NA protein can initiate entry. Prior to binding, NA proteins promote access to target cells by degrading mucous, which helps to remove extracellular decoy receptors that would impede access to target cells. After binding, the virus is internalized into the cell by an endosome that contains the virion inside it. The endosome is acidified by cellular vATPase to have lower pH, which triggers a conformational change in HA that allows fusion of the viral envelope with the endosomal membrane. At the same time, hydrogen ions diffuse into the virion through M2 ion channels, disrupting internal protein-protein interactions to release RNPs into the host cells cytosol. The M1 protein shell surrounding RNPs is degraded, fully uncoating RNPs in the cytosol.RNPs are then imported into the nucleus with the help of viral localization signals. There, the viral RNA polymerase transcribes mRNA using the genomic negative-sense strand as a template. The polymerase snatches 5 caps for viral mRNA from cellular RNA to prime mRNA synthesis and the 3-end of mRNA is polyadenylated at the end of transcription. Once viral mRNA is transcribed, it is exported out of the nucleus and translated by host ribosomes in a cap-dependent manner to synthesize viral proteins. RdRp also synthesizes complementary positive-sense strands of the viral genome in a complementary RNP complex which are then used as templates by viral polymerases to synthesize copies of the negative-sense genome. During these processes, RdRps of avian influenza viruses (AIVs) function optimally at a higher temperature than mammalian influenza viruses.Newly synthesized viral polymerase subunits and NP proteins are imported to the nucleus to further increase the rate of viral replication and form RNPs. HA, NA, and M2 proteins are trafficked with the aid of M1 and NEP proteins to the cell membrane through the Golgi apparatus and inserted into the cells membrane. Viral non-structural proteins including NS1, PB1-F2, and PA-X regulate host cellular processes to disable antiviral responses. PB1-F2 aso interacts with PB1 to keep polymerases in the nucleus longer. M1 and NEP proteins localize to the nucleus during the later stages of infection, bind to viral RNPs and mediate their export to the cytoplasm where they migrate to the cell membrane with the aid of recycled endosomes and are bundled into the segments of the genome.Progenic viruses leave the cell by budding from the cell membrane, which is initiated by the accumulation of M1 proteins at the cytoplasmic side of the membrane. The viral genome is incorporated inside a viral envelope derived from portions of the cell membrane that have HA, NA, and M2 proteins. At the end of budding, HA proteins remain attached to cellular sialic acid until they are cleaved by the sialidase activity of NA proteins. The virion is then released from the cell. The sialidase activity of NA also cleaves any sialic acid residues from the viral surface, which helps prevent newly assembled viruses from aggregating near the cell surface and improving infectivity. Similar to other aspects of influenza replication, optimal NA activity is temperature- and pH-dependent. Ultimately, presence of large quantities of viral RNA in the cell triggers apoptosis, i.e. programmed cell death, which is initiated by cellular factors to restrict viral replication. Antigenic drift and shift Two key processes that influenza viruses evolve through are antigenic drift and antigenic shift. Antigenic drift is when an influenza viruss antigens change due to the gradual accumulation of mutations in the antigens (HA or NA) gene. This can occur in response to evolutionary pressure exerted by the host immune response. Antigenic drift is especially common for the HA protein, in which just a few amino acid changes in the head region can constitute antigenic drift. The result is the production of novel strains that can evade pre-existing antibody-mediated immunity. Antigenic drift occurs in all influenza species but is slower in B than A and slowest in C and D. Antigenic drift is a major cause of seasonal influenza, and requires that flu vaccines be updated annually. HA is the main component of inactivated vaccines, so surveillance monitors antigenic drift of this antigen among circulating strains. Antigenic evolution of influenza viruses of humans appears to be faster than influenza viruses in swine and equines. In wild birds, within-subtype antigenic variation appears to be limited but has been observed in poultry.Antigenic shift is a sudden, drastic change in an influenza viruss antigen, usually HA. During antigenic shift, antigenically different strains that infect the same cell can reassort genome segments with each other, producing hybrid progeny. Since all influenza viruses have segmented genomes, all are capable of reassortment. Antigenic shift, however, only occurs among influenza viruses of the same genus and most commonly occurs among IAVs. In particular, reassortment is very common in AIVs, creating a large diversity of influenza viruses in birds, but is uncommon in human, equine, and canine lineages. Pigs, bats, and quails have receptors for both mammalian and avian IAVs, so they are potential "mixing vessels" for reassortment. If an animal strain reassorts with a human strain, then a novel strain can emerge that is capable of human-to-human transmission. This has caused pandemics, but only a limited number have occurred, so it is difficult to predict when the next will happen. Mechanism Transmission People who are infected can transmit influenza viruses through breathing, talking, coughing, and sneezing, which spread respiratory droplets and aerosols that contain virus particles into the air. A person susceptible to infection can then contract influenza by coming into contact with these particles. Respiratory droplets are relatively large and travel less than two meters before falling onto nearby surfaces. Aerosols are smaller and remain suspended in the air longer, so they take longer to settle and can travel further than respiratory droplets. Inhalation of aerosols can lead to infection, but most transmission is in the area about two meters around an infected person via respiratory droplets that come into contact with mucosa of the upper respiratory tract. Transmission through contact with a person, bodily fluids, or intermediate objects (fomites) can also occur, such as through contaminated hands and surfaces since influenza viruses can survive for hours on non-porous surfaces. If ones hands are contaminated, then touching ones face can cause infection.Influenza is usually transmissible from one day before the onset of symptoms to 5–7 days after. In healthy adults, the virus is shed for up to 3–5 days. In children and the immunocompromised, the virus may be transmissible for several weeks. Children ages 2–17 are considered to be the primary and most efficient spreaders of influenza. Children who have not had multiple prior exposures to influenza viruses shed the virus at greater quantities and for a longer duration than other children. People who are at risk of exposure to influenza include health care workers, social care workers, and those who live with or care for people vulnerable to influenza. In long-term care facilities, the flu can spread rapidly after it is introduced. A variety of factors likely encourage influenza transmission, including lower temperature, lower absolute and relative humidity, less ultraviolet radiation from the Sun, and crowding. Influenza viruses that infect the upper respiratory tract like H1N1 tend to be more mild but more transmissible, whereas those that infect the lower respiratory tract like H5N1 tend to cause more severe illness but are less contagious. Pathophysiology In humans, influenza viruses first cause infection by infecting epithelial cells in the respiratory tract. Illness during infection is primarily the result of lung inflammation and compromise caused by epithelial cell infection and death, combined with inflammation caused by the immune systems response to infection. Non-respiratory organs can become involved, but the mechanisms by which influenza is involved in these cases are unknown. Severe respiratory illness can be caused by multiple, non-exclusive mechanisms, including obstruction of the airways, loss of alveolar structure, loss of lung epithelial integrity due to epithelial cell infection and death, and degradation of the extracellular matrix that maintains lung structure. In particular, alveolar cell infection appears to drive severe symptoms since this results in impaired gas exchange and enables viruses to infect endothelial cells, which produce large quantities of pro-inflammatory cytokines.Pneumonia caused by influenza viruses is characterized by high levels of viral replication in the lower respiratory tract, accompanied by a strong pro-inflammatory response called a cytokine storm. Infection with H5N1 or H7N9 especially produces high levels of pro-inflammatory cytokines. In bacterial infections, early depletion of macrophages during influenza creates a favorable environment in the lungs for bacterial growth since these white blood cells are important in responding to bacterial infection. Host mechanisms to encourage tissue repair may inadvertently allow bacterial infection. Infection also induces production of systemic glucocorticoids that can reduce inflammation to preserve tissue integrity but allow increased bacterial growth.The pathophysiology of influenza is significantly influenced by which receptors influenza viruses bind to during entry into cells. Mammalian influenza viruses preferentially bind to sialic acids connected to the rest of the oligosaccharide by an α-2,6 link, most commonly found in various respiratory cells, such as respiratory and retinal epithelial cells. AIVs prefer sialic acids with an α-2,3 linkage, which are most common in birds in gastrointestinal epithelial cells and in humans in the lower respiratory tract. Furthermore, cleavage of the HA protein into HA1, the binding subunit, and HA2, the fusion subunit, is performed by different proteases, affecting which cells can be infected. For mammalian influenza viruses and low pathogenic AIVs, cleavage is extracellular, which limits infection to cells that have the appropriate proteases, whereas for highly pathogenic AIVs, cleavage is intracellular and performed by ubiquitous proteases, which allows for infection of a greater variety of cells, thereby contributing to more severe disease. Immunology Cells possess sensors to detect viral RNA, which can then induce interferon production. Interferons mediate expression of antiviral proteins and proteins that recruit immune cells to the infection site, and they also notify nearby uninfected cells of infection. Some infected cells release pro-inflammatory cytokines that recruit immune cells to the site of infection. Immune cells control viral infection by killing infected cells and phagocytizing viral particles and apoptotic cells. An exacerbated immune response, however, can harm the host organism through a cytokine storm. To counter the immune response, influenza viruses encode various non-structural proteins, including NS1, NEP, PB1-F2, and PA-X, that are involved in curtailing the host immune response by suppressing interferon production and host gene expression.B cells, a type of white blood cell, produce antibodies that bind to influenza antigens HA and NA (or HEF) and other proteins to a lesser degree. Once bound to these proteins, antibodies block virions from binding to cellular receptors, neutralizing the virus. In humans, a sizeable antibody response occurs ~1 week after viral exposure. This antibody response is typically robust and long-lasting, especially for ICV and IDV. In other words, people exposed to a certain strain in childhood still possess antibodies to that strain at a reasonable level later in life, which can provide some protection to related strains. There is, however, an "original antigenic sin", in which the first HA subtype a person is exposed to influences the antibody-based immune response to future infections and vaccines. Prevention Vaccination Annual vaccination is the primary and most effective way to prevent influenza and influenza-associated complications, especially for high-risk groups. Vaccines against the flu are trivalent or quadrivalent, providing protection against an H1N1 strain, an H3N2 strain, and one or two IBV strains corresponding to the two IBV lineages. Two types of vaccines are in use: inactivated vaccines that contain "killed" (i.e. inactivated) viruses and live attenuated influenza vaccines (LAIVs) that contain weakened viruses. There are three types of inactivated vaccines: whole virus, split virus, in which the virus is disrupted by a detergent, and subunit, which only contains the viral antigens HA and NA. Most flu vaccines are inactivated and administered via intramuscular injection. LAIVs are sprayed into the nasal cavity.Vaccination recommendations vary by country. Some recommend vaccination for all people above a certain age, such as 6 months, whereas other countries recommendation is limited for high at risk groups, such as pregnant women, young children (excluding newborns), the elderly, people with chronic medical conditions, health care workers, people who come into contact with high-risk people, and people who transmit the virus easily. Young infants cannot receive flu vaccines for safety reasons, but they can inherit passive immunity from their mother if inactivated vaccines are administered to the mother during pregnancy. Influenza vaccination also helps to reduce the probability of reassortment.In general, influenza vaccines are only effective if there is an antigenic match between vaccine strains and circulating strains. Additionally, most commercially available flu vaccines are manufactured by propagation of influenza viruses in embryonated chicken eggs, taking 6–8 months. Flu seasons are different in the northern and southern hemisphere, so the WHO meets twice a year, one for each hemisphere, to discuss which strains should be included in flu vaccines based on observation from HA inhibition assays. Other manufacturing methods include an MDCK cell culture-based inactivated vaccine and a recombinant subunit vaccine manufactured from baculovirus overexpression in insect cells. Antiviral chemoprophylaxis Influenza can be prevented or reduced in severity by post-exposure prophylaxis with the antiviral drugs oseltamivir, which can be taken orally by those at least three months old, and zanamivir, which can be inhaled by those above seven years of age. Chemoprophylaxis is most useful for individuals at high-risk of developing complications and those who cannot receive the flu vaccine due to contraindications or lack of effectiveness. Post-exposure chemoprophylaxis is only recommended if oseltamivir is taken within 48 hours of contact with a confirmed or suspected influenza case and zanamivir within 36 hours. It is recommended that it be offered to people who have yet to receive a vaccine for the current flu season, who have been vaccinated less than two week since contact, if there is a significant mismatch between vaccine and circulating strains, or during an outbreak in a closed setting regardless of vaccination history. Infection control Hand hygiene is important in reducing the spread of influenza. This includes frequent hand washing with soap and water, using alcohol-based hand sanitizers, and not touching ones eyes, nose, and mouth with ones hands. Covering ones nose and mouth when coughing or sneezing is important. Other methods to limit influenza transmission include staying home when sick, avoiding contact with others until one day after symptoms end, and disinfecting surfaces likely to be contaminated by the virus, such as doorknobs. Health education through media and posters is often used to remind people of the aforementioned etiquette and hygiene.There is uncertainty about the use of masks since research thus far has not shown a significant reduction in seasonal influenza with mask usage. Likewise, the effectiveness of screening at points of entry into countries is not well researched. Social distancing measures such as school closures, avoiding contact with infected people via isolation or quarantine, and limiting mass gatherings may reduce transmission, but these measures are often expensive, unpopular, and difficult to implement. Consequently, the commonly recommended methods of infection control are respiratory etiquette, hand hygiene, and mask wearing, which are inexpensive and easy to perform. Pharmaceutical measures are effective but may not be available in the early stages of an outbreak.In health care settings, infected individuals may be cohorted or assigned to individual rooms. Protective clothing such as masks, gloves, and gowns is recommended when coming into contact with infected individuals if there is a risk of exposure to infected bodily fluids. Keeping patients in negative pressure rooms and avoiding aerosol-producing activities may help, but special air handling and ventilation systems are not considered necessary to prevent the spread of influenza in the air. In residential homes, new admissions may need to be closed until the spread of influenza is controlled. When discharging patients to care homes, it is important to take care if there is a known influenza outbreak.Since influenza viruses circulate in animals such as birds and pigs, prevention of transmission from these animals is important. Water treatment, indoor raising of animals, quarantining sick animals, vaccination, and biosecurity are the primary measures used. Placing poultry houses and piggeries on high ground away from high-density farms, backyard farms, live poultry markets, and bodies of water helps to minimize contact with wild birds. Closure of live poultry markets appears to the most effective measure and has shown to be effective at controlling the spread of H5N1, H7N9, and H9N2. Other biosecurity measures include cleaning and disinfecting facilities and vehicles, banning visits to poultry farms, not bringing birds intended for slaughter back to farms, changing clothes, disinfecting foot baths, and treating food and water.If live poultry markets are not closed, then "clean

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days" when unsold poultry is removed and facilities are disinfected and "no carry-over" policies to eliminate infectious material before new poultry arrive can be used to reduce the spread of influenza viruses. If a novel influenza viruses has breached the aforementioned biosecurity measures, then rapid detection to stamp it out via quarantining, decontamination, and culling may be necessary to prevent the virus from becoming endemic. Vaccines exist for avian H5, H7, and H9 subtypes that are used in some countries. In China, for example, vaccination of domestic birds against H7N9 successfully limited its spread, indicating that vaccination may be an effective strategy if used in combination with other measures to limit transmission. In pigs and horses, management of influenza is dependent on vaccination with biosecurity. Diagnosis Diagnosis based on symptoms is fairly accurate in otherwise healthy people during seasonal epidemics and should be suspected in cases of pneumonia, acute respiratory distress syndrome (ARDS), sepsis, or if encephalitis, myocarditis, or breaking down of muscle tissue occur. Because influenza is similar to other viral respiratory tract illnesses, laboratory diagnosis is necessary for confirmation. Common ways of collecting samples for testing include nasal and throat swabs. Samples may be taken from the lower respiratory tract if infection has cleared the upper but not lower respiratory tract. Influenza testing is recommended for anyone hospitalized with symptoms resembling influenza during flu season or who is connected to an influenza case. For severe cases, earlier diagnosis improves patient outcome. Diagnostic methods that can identify influenza include viral cultures, antibody- and antigen-detecting tests, and nucleic acid-based tests.Viruses can be grown in a culture of mammalian cells or embryonated eggs for 3–10 days to monitor cytopathic effect. Final confirmation can then be done via antibody staining, hemadsorption using red blood cells, or immunofluorescence microscopy. Shell vial cultures, which can identify infection via immunostaining before a cytopathic effect appears, are more sensitive than traditional cultures with results in 1–3 days. Cultures can be used to characterize novel viruses, observe sensitivity to antiviral drugs, and monitor antigenic drift, but they are relatively slow and require specialized skills and equipment.Serological assays can be used to detect an antibody response to influenza after natural infection or vaccination. Common serological assays include hemagglutination inhibition assays that detect HA-specific antibodies, virus neutralization assays that check whether antibodies have neutralized the virus, and enzyme-linked immunoabsorbant assays. These methods tend to be relatively inexpensive and fast but are less reliable than nucleic-acid based tests.Direct fluorescent or immunofluorescent antibody (DFA/IFA) tests involve staining respiratory epithelial cells in samples with fluorescently-labeled influenza-specific antibodies, followed by examination under a fluorescent microscope. They can differentiate between IAV and IBV but cant subtype IAV. Rapid influenza diagnostic tests (RIDTs) are a simple way of obtaining assay results, are low cost, and produce results quickly, at less than 30 minutes, so they are commonly used, but they cant distinguish between IAV and IBV or between IAV subtypes and are not as sensitive as nucleic-acid based tests.Nucleic acid-based tests (NATs) amplify and detect viral nucleic acid. Most of these tests take a few hours, but rapid molecular assays are as fast as RIDTs. Among NATs, reverse transcription polymerase chain reaction (RT-PCR) is the most traditional and considered the gold standard for diagnosing influenza because it is fast and can subtype IAV, but it is relatively expensive and more prone to false-positives than cultures. Other NATs that have been used include loop-mediated isothermal amplification-based assays, simple amplification-based assays, and nucleic acid sequence-based amplification. Nucleic acid sequencing methods can identify infection by obtaining the nucleic acid sequence of viral samples to identify the virus and antiviral drug resistance. The traditional method is Sanger sequencing, but it has been largely replaced by next-generation methods that have greater sequencing speed and throughput. Treatment Treatment of influenza in cases of mild or moderate illness is supportive and includes anti-fever medications such as acetaminophen and ibuprofen, adequate fluid intake to avoid dehydration, and resting at home. Cough drops and throat sprays may be beneficial for sore throat. It is recommended to avoid alcohol and tobacco use while sick with the flu. Aspirin is not recommended to treat influenza in children due to an elevated risk of developing Reye syndrome. Corticosteroids likewise are not recommended except when treating septic shock or an underlying medical condition, such as chronic obstructive pulmonary disease or asthma exacerbation, since they are associated with increased mortality. If a secondary bacterial infection occurs, then treatment with antibiotics may be necessary. Antivirals Antiviral drugs are primarily used to treat severely ill patients, especially those with compromised immune systems. Antivirals are most effective when started in the first 48 hours after symptoms appear. Later administration may still be beneficial for those who have underlying immune defects, those with more severe symptoms, or those who have a higher risk of developing complications if these individuals are still shedding the virus. Antiviral treatment is also recommended if a person is hospitalized with suspected influenza instead of waiting for test results to return and if symptoms are worsening. Most antiviral drugs against influenza fall into two categories: neuraminidase (NA) inhibitors and M2 inhibitors. Baloxavir marboxil is a notable exception, which targets the endonuclease activity of the viral RNA polymerase and can be used as an alternative to NA and M2 inhibitors for IAV and IBV.NA inhibitors target the enzymatic activity of NA receptors, mimicking the binding of sialic acid in the active site of NA on IAV and IBV virions so that viral release from infected cells and the rate of viral replication are impaired. NA inhibitors include oseltamivir, which is consumed orally in a prodrug form and converted to its active form in the liver, and zanamivir, which is a powder that is inhaled nasally. Oseltamivir and zanamivir are effective for prophylaxis and post-exposure prophylaxis, and research overall indicates that NA inhibitors are effective at reducing rates of complications, hospitalization, and mortality and the duration of illness. Additionally, the earlier NA inhibitors are provided, the better the outcome, though late administration can still be beneficial in severe cases. Other NA inhibitors include laninamivir and peramivir, the latter of which can be used as an alternative to oseltamivir for people who cannot tolerate or absorb it.The adamantanes amantadine and rimantadine are orally administered drugs that block the influenza viruss M2 ion channel, preventing viral uncoating. These drugs are only functional against IAV but are no longer recommended for use because of widespread resistance to them among IAVs. Adamantane resistance first emerged in H3N2 in 2003, becoming worldwide by 2008. Oseltamivir resistance is no longer widespread because the 2009 pandemic H1N1 strain (H1N1 pdm09), which is resistant to adamantanes, seemingly replaced resistant strains in circulation. Since the 2009 pandemic, oseltamivir resistance has mainly been observed in patients undergoing therapy, especially the immunocompromised and young children. Oseltamivir resistance is usually reported in H1N1, but has been reported in H3N2 and IBVs less commonly. Because of this, oseltamivir is recommended as the first drug of choice for immunocompetent people, whereas for the immunocompromised, oseltamivir is recommended against H3N2 and IBV and zanamivir against H1N1 pdm09. Zanamivir resistance is observed less frequently, and resistance to peramivir and baloxavir marboxil is possible. Prognosis In healthy individuals, influenza infection is usually self-limiting and rarely fatal. Symptoms usually last for 2–8 days. Influenza can cause people to miss work or school, and it is associated with decreased job performance and, in older adults, reduced independence. Fatigue and malaise may last for several weeks after recovery, and healthy adults may experience pulmonary abnormalities that can take several weeks to resolve. Complications and mortality primarily occur in high-risk populations and those who are hospitalized. Severe disease and mortality are usually attributable to pneumonia from the primary viral infection or a secondary bacterial infection, which can progress to ARDS.Other respiratory complications that may occur include sinusitis, bronchitis, bronchiolitis, excess fluid buildup in the lungs, and exacerbation of chronic bronchitis and asthma. Middle ear infection and croup may occur, most commonly in children. Secondary S. aureus infection has been observed, primarily in children, to cause toxic shock syndrome after influenza, with hypotension, fever, and reddening and peeling of the skin. Complications affecting the cardiovascular system are rare and include pericarditis, fulminant myocarditis with a fast, slow, or irregular heartbeat, and exacerbation of pre-existing cardiovascular disease. Inflammation or swelling of muscles accompanied by muscle tissue breaking down occurs rarely, usually in children, which presents as extreme tenderness and muscle pain in the legs and a reluctance to walk for 2–3 days.Influenza can affect pregnancy, including causing smaller neonatal size, increased risk of premature birth, and an increased risk of child death shortly before or after birth. Neurological complications have been associated with influenza on rare occasions, including aseptic meningitis, encephalitis, disseminated encephalomyelitis, transverse myelitis, and Guillain–Barré syndrome. Additionally, febrile seizures and Reye syndrome can occur, most commonly in children. Influenza-associated encephalopathy can occur directly from central nervous system infection from the presence of the virus in blood and presents as suddent onset of fever with convulsions, followed by rapid progression to coma. An atypical form of encephalitis called encephalitis lethargica, characterized by headache, drowsiness, and coma, may rarely occur sometime after infection. In survivors of influenza-associated encephalopathy, neurological defects may occur. Primarily in children, in severe cases the immune system may rarely dramatically overproduce white blood cells that release cytokines, causing severe inflammation.People who are at least 65 years of age, due to a weakened immune system from aging or a chronic illness, are a high-risk group for developing complications, as are children less than one year of age and children who have not been previously exposed to influenza viruses multiple times. Pregnant women are at an elevated risk, which increases by trimester and lasts up to two weeks after childbirth. Obesity, in particular a body mass index greater than 35–40, is associated with greater amounts of viral replication, increased severity of secondary bacterial infection, and reduced vaccination efficacy. People who have underlying health conditions are also considered at-risk, including those who have congenital or chronic heart problems or lung (e.g. asthma), kidney, liver, blood, neurological, or metabolic (e.g. diabetes) disorders, as are people who are immunocompromised from chemotherapy, asplenia, prolonged steroid treatment, splenic dysfunction, or HIV infection. Current or past tobacco use also places a person at risk. The role of genetics in influenza is not well researched, but it may be a factor in influenza mortality. Epidemiology Influenza is typically characterized by seasonal epidemics and sporadic pandemics. Most of the burden of influenza is a result of flu seasons caused by IAV and IBV. Among IAV subtypes, H1N1 and H3N2 currently circulate in humans and are responsible for seasonal influenza. Cases disproportionately occur in children, but most severe causes are among the elderly, the very young, and the immunocompromised. In a typical year, influenza viruses infect 5–15% of the global population, causing 3–5 million cases of severe illness annually and accounting for 290,000–650,000 deaths each year due to respiratory illness. 5–10% of adults and 20–30% of children contract influenza each year. The reported number of influenza cases is usually much lower than the actual number of cases.During seasonal epidemics, it is estimated that about 80% of otherwise healthy people who have a cough or sore throat have the flu. Approximately 30–40% of people hospitalized for influenza develop pneumonia, and about 5% of all severe pneumonia cases in hospitals are due to influenza, which is also the most common cause of ARDS in adults. In children, influenza is one of the two most common causes of ARDS, the other being the respiratory syncytial virus. About 3–5% of children each year develop otitis media due to influenza. Adults who develop organ failure from influenza and children who have PIM scores and acute renal failure have higher rates of mortality. During seasonal influenza, mortality is concentrated in the very young and the elderly, whereas during flu pandemics, young adults are often affected at a high rate. In temperate regions, the number of influenza cases varies from season to season. Lower vitamin D levels, presumably due to less sunlight, lower humidity, lower temperature, and minor changes in virus proteins caused by antigenic drift contribute to annual epidemics that peak during the winter season. In the northern hemisphere, this is from October to May (more narrowly December to April), and in the southern hemisphere, this is from May to October (more narrowly June to September). There are therefore two distinct influenza seasons every year in temperate regions, one in the northern hemisphere and one in the southern hemisphere. In tropical and subtropical regions, seasonality is more complex and appears to be affected by various climatic factors such as minimum temperature, hours of sunshine, maximum rainfall, and high humidity. Influenza may therefore occur year-round in these regions. Influenza epidemics in modern times have the tendency to start in the eastern or southern hemisphere, with Asia being a key reservoir of influenza viruses.IAV and IBV co-circulate, so the two have the same patterns of transmission. The seasonality of ICV, however, is poorly understood. ICV infection is most common in children under the age of 2, and by adulthood most people have been exposed to it. ICV-associated hospitalization most commonly occurs in children under the age of 3 and is frequently accompanied by co-infection with another virus or a bacterium, which may increase the severity of disease. When considering all hospitalizations for respiratory illness among young children, ICV appears to account for only a small percentage of such cases. Large outbreaks of ICV infection can occur, so incidence varies significantly.Outbreaks of influenza caused by novel influenza viruses are common. Depending on the level of pre-existing immunity in the population, novel influenza viruses can spread rapidly and cause pandemics with millions of deaths. These pandemics, in contrast to seasonal influenza, are caused by antigenic shifts involving animal influenza viruses. To date, all known flu pandemics have been caused by IAVs, and they follow the same pattern of spreading from an origin point to the rest of the world over the course of multiple waves in a year. Pandemic strains tend to be associated with higher rates of pneumonia in otherwise healthy individuals. Generally after each influenza pandemic, the pandemic strain continues to circulate as the cause of seasonal influenza, replacing prior strains. From 1700 to 1889, influenza pandemics occurred about once every 50–60 years. Since then, pandemics have occurred about once every 10–50 years, so they may be getting more frequent over time. History It is impossible to know when an influenza virus first infected humans or when the first influenza pandemic occurred. Possibly the first influenza epidemic occurred around 6,000 BC in China, and possible descriptions of influenza exist in Greek writings from the 5th century BC. In both 1173–1174 AD and 1387 AD, epidemics occurred across Europe that were named "influenza". Whether these epidemics and others were caused by influenza is unclear since there was no consistent naming pattern for epidemic respiratory diseases at that time, and "influenza" didnt become completely attached to respiratory disease until centuries later. Influenza may have been brought to the Americas as early as 1493, when an epidemic disease resembling influenza killed most of the population of the Antilles.The first convincing record of an influenza pandemic was chronicled in 1510; it began in East Asia before spreading to North Africa and then Europe. Following the pandemic, seasonal influenza occurred, with subsequent pandemics in 1557 and 1580. The flu pandemic in 1557 was potentially the first time influenza was connected to miscarriage and death of pregnant women. The 1580 flu pandemic originated in Asia during summer, spread to Africa, then Europe, and finally America. By the end of the 16th century, influenza was likely beginning to become understood as a specific, recognizable disease with epidemic and endemic forms. In 1648, it was discovered that horses also experience influenza.Influenza data after 1700 is more informative, so it is easier to identify flu pandemics after this point, each of which incrementally increased understanding of influenza. The first flu pandemic of the 18th century started in 1729 in Russia in spring, spreading worldwide over the course of three years with distinct waves, the later ones being more lethal. The second flu pandemic of the 18th century was in 1781–1782, starting in China in autumn. From this pandemic, influenza became associated with sudden outbreaks of febrile illness. The next flu pandemic was from 1830 to 1833, beginning in China in winter. This pandemic had a high attack rate, but the mortality rate was low.A minor influenza pandemic occurred from 1847 to 1851 at the same time as the third cholera pandemic and was the first flu pandemic to occur with vital statistics being recorded, so influenza mortality was clearly recorded for the first time. Highly pathogenic avian influenza was recognized in 1878 and was soon linked to transmission to humans. By the time of the 1889 pandemic, which may have been caused by an H2N2 strain, the flu had become an easily recognizable disease.Initially, the microbial agent responsible for influenza was incorrently identified in 1892 by R. F. J. Pfeiffer as the bacteria species Haemophilus influenzae, which retains "influenza" in its name. In the following years, the field of virology began to form as viruses were identified as the cause of many diseases. From 1901 to 1903, Italian and Austrian researchers were able to show that avian influenza, then called "fowl plague", was caused by a microscopic agent smaller than bacteria by using filters with pores too small for bacteria to pass through. The fundamental differences between viruses and bacteria, however, were not yet fully understood. From 1918 to 1920, the Spanish flu pandemic became the most devastating influenza pandemic and one of the deadliest pandemics in history. The pandemic, probably caused by H1N1, likely began in the USA before spreading worldwide by soldiers during and after the First World War. The initial wave in the first half of 1918 was relatively minor and resembled past flu pandemics, but the second wave later that year had a much higher mortality rate, accounting for most deaths. A third wave with lower mortality occurred in many places a few months after the second. By the end of 1920, it is estimated that about a third to half of all people in the world had been infected, with tens of millions of deaths, disproportionately young adults. During the 1918 pandemic, the respiratory route of transmission was clearly identified and influenza was shown to be caused by a "filter passer", not a bacterium, but there remained a lack of agreement about influenzas cause for another decade and research on influenza declined. After the pandemic, H1N1 circulated in humans in seasonal form up until the next pandemic.In 1931, Richard Shope published three papers identifying a virus as the cause of swine influenza, a then newly recognized disease among pigs that was first characterized during the second wave of the 1918 pandemic. Shopes research reinvigorated research on human influenza, and many advances in virology, serology, immunology, experimental animal models, vaccinology, and immunotherapy have since arisen from influenza research. Just two years after influenza viruses were discovered, in 1933, IAV was identified as the agent responsible for human influenza. Subtypes of IAV were discovered throughout the 1930s, and IBV was discovered in 1940.During the Second World War, the US government worked on developing inactivated vaccines for influenza, resulting in the first influenza vaccine being licensed in 1945 in the United States. ICV was discovered two years later in 1947. In 1955, avian influenza was confirmed to be caused by IAV. Four influenza pandemics have occurred since WWII, each less severe than the 1918 pandemic. The first of these was the Asian flu from 1957 to 1958, caused by an H2N2 strain and beginning in Chinas Yunnan province. The number of deaths probably exceeded one million, mostly among the very young and very old. Notably, the 1957 pandemic was the first flu pandemic to occur in the presence of a global surveillance system and laboratories able to study the novel influenza virus. After the pandemic, H2N2 was the IAV subtype responsible for seasonal influenza. The first antiviral drug against influenza, amantadine, was approved for use in 1966, with additional antiviral drugs being used since the 1990s.In 1968, H3N2 was introduced into humans as a result of a reassortment between an avian H3N2 strain and an H2N2 strain that was circulating in humans. The novel H3N2 strain first emerged in Hong Kong and spread worldwide, causing the Hong Kong flu pandemic, which resulted in 500,000–2,000,000 deaths. This was the first pandemic to spread significantly by air travel. H2N2 and H3N2 co-circulated after the pandemic until 1971 when H2N2 waned in prevalence and was completely replaced by H3N2. In 1977, H1N1 reemerged in humans, possibly after it was released from a freezer in a laboratory accident, and caused a pseudo-pandemic. Whether the 1977 "pandemic" deserves to be included in the natural history of flu pandemics is debatable. This H1N1 strain was antigenically similar to the H1N1 strains that circulated prior to 1957. Since 1977, both H1N1 and H3N2 have circulated in humans as part of seasonal influenza. In 1980, the current classification system used to subtype influenza viruses was introduced. At some point, IBV diverged into two lineages, named the B/Victoria-like and B/Yamagata-like lineages, both of which have been circulating in humans since 1983. In 1996, HPAI H5N1 was detected in Guangdong, China and a year later emerged in poultry in Hong Kong, gradually spreading worldwide from there. A small H5N1 outbreak in humans in Hong Kong occurred then, and sporadic human cases have occurred since 1997, carrying a high case fatality rate. The most recent flu pandemic was the 2009 swine flu pandemic, which originated in Mexico and resulted in hundreds of thousands of deaths. It was caused by a novel H1N1 strain that was a reassortment of human, swine, and avian influenza viruses. The 2009 pandemic had the effect of replacing prior H1N1 strains in circulation with the novel strain but not any other influenza viruses. Consequently, H1N1, H3N2, and both IBV lineages have been in circulation in seasonal form since the 2009 pandemic.In 2011, IDV was discovered in pigs in Oklahoma, USA, and cattle were later identified as the primary reservoir of IDV. In the same year, avian H7N9 was detected in China and began to cause human infections in 2013, starting in Shanghai and Anhui and remaining mostly in China. HPAI H7N9 emerged sometime in 2016 and has occasionally infected humans incidentally. Other AIVs have less commonly infected humans since the 1990s, including H5N6, H6N1, H7N2-4, H7N7, and H10N7-8, and HPAI H subtypes such as H5N1-3, H5N5-6, and H5N8 have begun to spread throughout much of the world since the 2010s. Future flu pandemics, which may be caused by an influenza virus of avian origin, are viewed as almost inevitable, and increased globalization has made it easier for novel viruses to spread, so there are continual efforts to prepare for future pandemics and improve the prevention and treatment of influenza. Etymology The word influenza comes from the Italian word influenza, from medieval Latin influentia, originally meaning "visitation" or "influence". Terms such as influenza di freddo, meaning "influence of the cold", and influenza di stelle, meaning "influence of the stars" are attested from the 14th century. The latter referred to the diseases cause, which at the time was ascribed by some to unfavorable astrological conditions. As early as 1504, influenza began to mean a "visitation" or "outbreak" of any disease affecting many people in a single place at once. During an outbreak of influenza in 1743 that started in Italy and spread throughout Europe, the word reached the English language and was anglicized in pronunciation. Since the mid-1800s, influenza has also been used to refer to severe colds. The shortened form of the word, "(the) flu", is first attested in 1839 as flue with the spelling flu first attested in 1893. Other names that have been used for influenza include epidemic catarrh, la grippe from French, sweating sickness, and, especially when referring to the 1918 pandemic strain, Spanish fever. Research Influenza research is wide-ranging and includes efforts to understand how influenza viruses enter hosts, the relationship between influenza viruses and bacteria, how influenza symptoms progress, and what make some influenza viruses deadlier than others. Non-structural proteins encoded by influenza viruses are periodically discovered and their functions are continually under research. Past pandemics, and especially the 1918 pandemic, are the subject of much research to understand flu pandemics. As part of pandemic preparedness, the Global Influenza Surveillance and Response System is a global network of laboratories that monitors influenza transmission and epidemiology. Additional areas of research include ways to improve the diagnosis, treatment, and prevention of influenza. Existing diagnostic methods have a variety of limitations coupled with their advantages. For example, NATs have high sensitivity and specificity but are impractical in under-resourced regions due to their high cost, complexity, maintenance, and training required. Low-cost, portable RIDTs can rapidly diagnose influenza but have highly variable sensitivity and are unable to subtype IAV. As a result of these limitations and others, research into new diagnostic methods revolves around producing new methods that are cost-effective, less labor-intensive, and less complex than existing methods while also being able to differentiate influenza species and IAV subtypes. One approach in development are lab-on-a-chips, which are diagnostic devices that make use of a variety of diagnostic tests, such as RT-PCR and serological assays, in microchip form. These chips have many potential advantages, including high reaction efficiency, low energy consumption, and low waste generation.New antiviral drugs are also in development due to the elimination of adamantines as viable drugs and concerns over oseltamivir resistance. These include: NA inhibitors that can be injected intravenously, such as intravenous formulations of zanamivir; favipiravir, which is a polymerase inhibitor used against several RNA viruses; pimodivir, which prevents cap-binding required during viral transcription; and nitazoxanide, which inhibits HA maturation. Reducing excess inflammation in the respiratory tract is also subject to much research since this is

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one of the primary mechanisms of influenza pathology. Other forms of therapy in development include monoclonal and polyclonal antibodies that target viral proteins, convalescent plasma, different approaches to modify the host antiviral response, and stem cell-based therapies to repair lung damage.Much research on LAIVs focuses on identifying genome sequences that can be deleted to create harmless influenza viruses in vaccines that still confer immunity. The high variability and rapid evolution of influenza virus antigens, however, is a major obstacle in developing effective vaccines. Furthermore, it is hard to predict which strains will be in circulation during the next flu season, manufacturing a sufficient quantity of flu vaccines for the next season is difficult, LAIVs have limited efficacy, and repeated annual vaccination potentially has diminished efficacy. For these reasons, "broadly-reactive" or "universal" flu vaccines are being researched that can provide protection against many or all influenza viruses. Approaches to develop such a vaccine include HA stalk-based methods such as chimeras that have the same stalk but different heads, HA head-based methods such as computationally optimized broadly neutralizing antigens, anti-idiotypic antibodies, and vaccines to elicit immune responses to highly conserved viral proteins. mRNA vaccines to provide protection against influenza are also under research. In animals Birds Aquatic birds such as ducks, geese, shorebirds, and gulls are the primary reservoir of IAVs. In birds, AIVs may be either low pathogenic avian influenza (LPAI) viruses that produce little to no symptoms or highly pathogenic avian influenza (HPAI) viruses that cause severe illness. Symptoms of HPAI infection include lack of energy and appetite, decreased egg production, soft-shelled or misshapen eggs, swelling of the head, comb, wattles, and hocks, purple discoloration of wattles, combs, and legs, nasal discharge, coughing, sneezing, incoordination, and diarrhea. Birds infected with an HPAI virus may also die suddenly without any signs of infection.The distinction between LPAI and HPAI can generally be made based on how lethal an AIV is to chickens. At the genetic level, an AIV can be usually be identified as an HPAI virus if it has a multibasic cleavage site in the HA protein, which contains additional residues in the HA gene. Most AIVs are LPAI. Notable HPAI viruses include HPAI H5N1 and HPAI H7N9. HPAI viruses have been a major disease burden in the 21st century, resulting in the death of large numbers of birds. In H7N9s case, some circulating strains were originally LPAI but became HPAI by acquiring the HA multibasic cleavage site. Avian H9N2 is also of concern because although it is LPAI, it is a common donor of genes to H5N1 and H7N9 during reassortment.Migratory birds can spread influenza across long distances. An example of this was when an H5N1 strain in 2005 infected birds at Qinghai Lake, China, which is a stopover and breeding site for many migratory birds, subsequently spreading the virus to more than 20 countries across Asia, Europe, and the Middle East. AIVs can be transmitted from wild birds to domestic free-range ducks and in turn to poultry through contaminated water, aerosols, and fomites. Ducks therefore act as key intermediates between wild and domestic birds. Transmission to poultry typically occurs in backyard farming and live animal markets where multiple species interact with each other. From there, AIVs can spread to poultry farms in the absence of adequate biosecurity. Among poultry, HPAI transmission occurs through aerosols and contaminated feces, cages, feed, and dead animals. Back-transmission of HPAI viruses from poultry to wild birds has occurred and is implicated in mass die-offs and intercontinental spread.AIVs have occasionally infected humans through aerosols, fomites, and contaminated water. Direction transmission from wild birds is rare. Instead, most transmission involves domestic poultry, mainly chickens, ducks, and geese but also a variety of other birds such as guinea fowl, partridge, pheasants, and quails. The primary risk factor for infection with AIVs is exposure to birds in farms and live poultry markets. Typically, infection with an AIV has an incubation period of 3–5 days but can be up to 9 days. H5N1 and H7N9 cause severe lower respiratory tract illness, whereas other AIVs such as H9N2 cause a more mild upper respiratory tract illness, commonly with conjunctivitis. Limited transmission of avian H2, H5-7, H9, and H10 subtypes from one person to another through respiratory droplets, aerosols, and fomites has occurred, but sustained human-to-human transmission of AIVs has not occurred. Before 2013, H5N1 was the most common AIV to infect humans. Since then, H7N9 has been responsible for most human cases. Pigs Influenza in pigs is a respiratory disease similar to influenza in humans and is found worldwide. Asymptomatic infections are common. Symptoms typically appear 1–3 days after infection and include fever, lethargy, anorexia, weight loss, labored breathing, coughing, sneezing, and nasal discharge. In sows, pregnancy may be aborted. Complications include secondary infections and potentially fatal bronchopneumonia. Pigs become contagious within a day of infection and typically spread the virus for 7–10 days, which can spread rapidly within a herd. Pigs usually recover from infection within 3–7 days after symptoms appear. Prevention and control measures include inactivated vaccines and culling infected herds. The influenza viruses usually responsible for swine flu are IAV subtypes H1N1, H1N2, and H3N2.Some IAVs can be transmitted via aerosols from pigs to humans and vice versa. Furthermore, pigs, along with bats and quails, are recognized as a mixing vessel of influenza viruses because they have both α-2,3 and α-2,6 sialic acid receptors in their respiratory tract. Because of that, both avian and mammalian influenza viruses can infect pigs. If co-infection occurs, then reassortment is possible. A notable example of this was the reassortment of a swine, avian, and human influenza virus in 2009, resulting in a novel H1N1 strain that caused the 2009 flu pandemic. Spillover events from humans to pigs, however, appear to be more common than from pigs to humans. Other animals Influenza viruses have been found in many other animals, including cattle, horses, dogs, cats, and marine mammals. Nearly all IAVs are apparently descended from ancestral viruses in birds. The exception are bat influenza-like viruses, which have an uncertain origin. These bat viruses have HA and NA subtypes H17, H18, N10, and N11. H17N10 and H18N11 are unable to reassort with other IAVs, but they are still able to replicate in other mammals. AIVs sometimes crossover into mammals. For example, in late 2016 to early 2017, an avian H7N2 strain was found to be infecting cats in New York.Equine IAVs include H7N7 and two lineages of H3N8. H7N7, however, has not been detected in horses since the late 1970s, so it may have become extinct in horses. H3N8 in equines spreads via aerosols and causes respiratory illness. Equine H3N8 perferentially binds to α-2,3 sialic acids, so horses are usually considered dead-end hosts, but transmission to dogs and camels has occurred, raising concerns that horses may be mixing vessels for reassortment. In canines, the only IAVs in circulation are equine-derived H3N8 and avian-derived H3N2. Canine H3N8 has not been observed to reassort with other subtypes. H3N2 has a much broader host range and can reassort with H1N1 and H5N1. An isolated case of H6N1 likely from a chicken was found infecting a dog, so other AIVs may emerge in canines.Other mammals to be infected by IAVs include H7N7 and H4N5 in seals, H1N3 in whales, and H10N4 and H3N2 in minks. Various mutations have been identified that are associated with AIVs adapting to mammals. Since HA proteins vary in which sialic acids they bind to, mutations in the HA receptor binding site can allow AIVs to infect mammals. Other mutations include mutations affecting which sialic acids NA proteins cleave and a mutation in the PB2 polymerase subunit that improves tolerance of lower temperatures in mammalian respiratory tracts and enhances RNP assembly by stabilizing NP and PB2 binding.IBV is mainly found in humans but has also been detected in pigs, dogs, horses, and seals. Likewise, ICV primarily infects humans but has been observed in pigs, dogs, cattle, and dromedary camels. IDV causes an influenza-like illness in pigs but its impact in its natural reservoir, cattle, is relatively unknown. It may cause respiratory disease resembling human influenza on its own, or it may be part of a bovine respiratory disease (BRD) complex with other pathogens during co-infection. BRD is a concern for the cattle industry, so IDVs possible involvement in BRD has led to research on vaccines for cattle that can provide protection against IDV. Two antigenic lineages are in circulation: D/swine/Oklahoma/1334/2011 (D/OK) and D/bovine/Oklahoma/660/2013 (D/660). == References ==

Meningism

Meningism is a set of symptoms similar to those of meningitis but not caused by meningitis. Whereas meningitis is inflammation of the meninges (membranes that cover the central nervous system), meningism is caused by nonmeningitic irritation of the meninges, usually associated with acute febrile illness, especially in children and adolescents. Meningism involves the triad (3-symptom syndrome) of nuchal rigidity (neck stiffness), photophobia (intolerance of bright light) and headache. It therefore requires differentiating from other CNS problems with similar symptoms, including meningitis and some types of intracranial hemorrhage. Related clinical signs include Kernigs sign and three signs all named Brudzinskis sign. Although nosologic coding systems, such as ICD-10 and MeSH, define meningism/meningismus as meningitis-like but in fact not meningitis, many physicians use the term meningism in a loose sense clinically to refer to any meningitis-like set of symptoms before the cause is definitively known. In this sense, the word implies "suspected meningitis". The words meningeal symptoms can be used instead to avoid ambiguity, thus reserving the term meningism for its strict sense. Signs and symptoms The main clinical signs that indicate meningism are nuchal rigidity, Kernigs sign and Brudzinskis signs. None of the signs are particularly sensitive; in adults with meningitis, nuchal rigidity was present in 30% and Kernigs or Brudzinskis sign only in 5%. Nuchal rigidity Nuchal rigidity is the inability to flex the neck forward due to rigidity of the neck muscles; if flexion of the neck is painful but full range of motion is present, nuchal rigidity is absent. Kernigs sign Kernigs sign (after Waldemar Kernig (1840–1917), a Russian neurologist) is positive when the thigh is flexed at the hip and knee at 90 degree angles, and subsequent extension in the knee is painful (leading to resistance). This may indicate subarachnoid hemorrhage or meningitis. Patients may also show opisthotonus—spasm of the whole body that leads to legs and head being bent back and body bowed forward. Brudzinskis signs Jozef Brudzinski (1874–1917), a Polish pediatrician, is credited with several signs in meningitis. The most commonly used sign (Brudzinskis neck sign) is positive when the forced flexion of the neck elicits a reflex flexion of the hips, with the patient lying supine.Other signs attributed to Brudzinski: The symphyseal sign, in which pressure on the pubic symphysis leads to abduction of the leg and reflexive hip and knee flexion. The cheek sign, in which pressure on the cheek below the zygoma leads to rising and flexion in the forearm. Brudzinskis reflex, in which passive flexion of one knee into the abdomen leads to involuntary flexion in the opposite leg, and stretching of a limb that was flexed leads to contralateral extension. See also Meningitis Meningoencephalitis References External links FPnotebook page on meningeal signs Image of Kernigs sign

Unstable angina

Unstable angina (UA), also called crescendo angina, is a type of angina pectoris that is irregular. It is also classified as a type of acute coronary syndrome (ACS).It can be difficult to distinguish unstable angina from non-ST elevation (non-Q wave) myocardial infarction (NSTEMI). They differ primarily in whether the ischemia is severe enough to cause sufficient damage to the hearts muscular cells to release detectable quantities of a marker of injury (typically troponin T or troponin I). Unstable angina is considered to be present in patients with ischemic symptoms suggestive of an ACS and no elevation in troponin, with or without ECG changes indicative of ischemia (e.g., ST segment depression or transient elevation or new T wave inversion). Since an elevation in troponin may not be detectable for up to 12 hours after presentation, UA and NSTEMI are frequently indistinguishable at initial evaluation. Signs and symptoms Pathophysiology The pathophysiology of unstable angina is controversial. Until recently, unstable angina was assumed to be angina pectoris caused by disruption of an atherosclerotic plaque with partial thrombosis and possibly embolization or vasospasm leading to myocardial ischemia. However, sensitive troponin assays reveal rise of cardiac troponin in the bloodstream with episodes of even mild myocardial ischemia. Since unstable angina is assumed to occur in the setting of acute myocardial ischemia without troponin release, the concept of unstable angina is being questioned with some calling for retiring the term altogether. Diagnosis Unstable angina is characterized by at least one of the following: Occurs at rest or minimal exertion and usually lasts more than 20 minutes (if nitroglycerin is not administered) Being severe (at least Canadian Cardiovascular Society Classification 3) and of new onset (i.e. within 1 month) Occurs with a crescendo pattern (brought on by less activity, more severe, more prolonged or increased frequency than previously).Fifty percent of people with unstable angina will have evidence of necrosis of the hearts muscular cells based on elevated cardiac serum markers such as creatine kinase isoenzyme (CK)-MB and troponin T or I, and thus have a diagnosis of non-ST elevation myocardial infarction. Management Nitroglycerin can be used immediately to dilate the venous system and reduce the circulating blood volume, therefore reducing the work and oxygen demand of the heart. In addition, nitroglycerin causes peripheral venous and artery dilation reducing cardiac preload and afterload. These reductions allow for decreased stress on the heart and therefore lower the oxygen demand of the hearts muscle cells.Antiplatelet drugs such as aspirin and clopidogrel can reduce platelet aggregation at the unstable atherosclerotic plaque, as well as combining these with an anticoagulant such as a low molecular weight heparin, can reduce clot formation. See also Variant angina References == External links ==

Sclera

The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and some other vertebrates, the whole sclera is white, contrasting with the coloured iris, but in most mammals, the visible part of the sclera matches the colour of the iris, so the white part does not normally show while other vertebrates have distinct colors for both of them. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow. People with dark skin can have naturally darkened sclerae, the result of melanin pigmentation.The human eye is relatively rare for having a pale sclera (relative to the iris). This makes it easier for one individual to identify where another individual is looking, and the cooperative eye hypothesis suggests this has evolved as a method of nonverbal communication. Structure The sclera forms the posterior five-sixths of the connective tissue coat of the globe. It is continuous with the dura mater and the cornea, and maintains the shape of the globe, offering resistance to internal and external forces, and provides an attachment for the extraocular muscle insertions. The sclera is perforated by many nerves and vessels passing through the posterior scleral foramen, the hole that is formed by the optic nerve. At the optic disc the outer two-thirds of the sclera continues with the dura mater (outer coat of the brain) via the dural sheath of the optic nerve. The inner third joins with some choroidal tissue to form a plate (lamina cribrosa) across the optic nerve with perforations through which the optic fibers (fasciculi) pass. The thickness of the sclera varies from 1 mm at the posterior pole to 0.3 mm just behind the rectus muscle insertions. The scleras blood vessels are mainly on the surface. Along with the vessels of the conjunctiva (which is a thin layer covering the sclera), those in the episclera render the inflamed eye bright red.In many vertebrates, the sclera is reinforced with plates of cartilage or bone, together forming a circular structure called the sclerotic ring. In primitive fish, this ring consists of four plates, but the number is lower in many living ray-finned fishes, and much higher in lobe-finned fishes, various reptiles, and birds. The ring has disappeared in many groups, including living amphibians, some reptiles and fish, and all mammals.The eyes of all non-human primates are dark with small, barely visible sclera. Histology The collagen of the sclera is continuous with the cornea. From outer to innermost, the four layers of the sclera are: episclera stroma lamina fusca endotheliumThe sclera is opaque due to the irregularity of the Type I collagen fibers, as opposed to the near-uniform thickness and parallel arrangement of the corneal collagen. Moreover, the cornea bears more mucopolysaccharide (a carbohydrate that has among its repeating units a nitrogenous sugar, hexosamine) to embed the fibrils. The cornea, unlike the sclera, has five layers. The middle, thickest layer is also called the stroma. The sclera, like the cornea, contains a basal endothelium, above which there is the lamina fusca, containing a high count of pigment cells.Sometimes, very small gray-blue spots can appear on the sclera, a harmless condition called scleral melanocytosis. Function Human eyes are somewhat distinctive in the animal kingdom in that the sclera is very plainly visible whenever the eye is open. This is not just due to the white color of the human sclera, which many other species share, but also to the fact that the human iris is relatively small and comprises a significantly smaller portion of the exposed eye surface compared to other animals. It is theorized that this adaptation evolved because of our social nature as the eye became a useful communication tool in addition to a sensory organ. It is believed that the conspicuous sclera of the human eye makes it easier for one individual to identify where another individual is looking, increasing the efficacy of this particular form of nonverbal communication, called cooperative eye hypothesis. Animal researchers have also found that, in the course of their domestication, dogs have also developed the ability to pick up visual cues from the eyes of humans. Dogs do not seem to use this form of communication with one another and only look for visual information from the eyes of humans. Injury Trauma The bony area that makes up the human eye socket provides exceptional protection to the sclera. However, if the sclera is ruptured by a blunt force or is penetrated by a sharp object, the recovery of full former vision is usually rare. If pressure is applied slowly, the eye is actually very elastic. However, most ruptures involve objects moving at some velocity. The cushion of orbital fat protects the sclera from head-on blunt forces, but damage from oblique forces striking the eye from the side is not prevented by this cushion. Hemorrhaging and a dramatic drop in intraocular pressure are common, along with a reduction in visual perception to only broad hand movements and the presence or absence of light. However, a low-velocity injury which does not puncture and penetrate the sclera requires only superficial treatment and the removal of the object. Sufficiently small objects which become embedded and which are subsequently left untreated may eventually become surrounded by a benign cyst, causing no other damage or discomfort. Thermal trauma The sclera is rarely damaged by brief exposure to heat: the eyelids provide exceptional protection, and the fact that the sclera is covered in layers of moist tissue means that these tissues are able to cause much of the offending heat to become dissipated as steam before the sclera itself is damaged. Even relatively low-temperature molten metals when splashed against an open eye have been shown to cause very little damage to the sclera, even while creating detailed casts of the surrounding eyelashes. Prolonged exposure, however—on the order of 30 seconds—at temperatures above 45 °C (113 °F) will begin to cause scarring, and above 55 °C (131 °F) will cause extreme changes in the sclera and surrounding tissue. Such long exposures even in industrial settings are virtually nonexistent. Chemical injury The sclera is highly resistant to injury from brief exposure to toxic chemicals. The reflexive production of tears at the onset of chemical exposure tends to quickly wash away such irritants, preventing further harm. Acids with a pH below 2.5 are the source of greatest acidic burn risk, with sulfuric acid, the kind present in car batteries and therefore commonly available, being among the most dangerous in this regard. However, acid burns, even severe ones, seldom result in loss of the eye.Alkali burns, on the other hand, such as those resulting from exposure to ammonium hydroxide or ammonium chloride or other chemicals with a pH above 11.5, will cause cellular tissue in the sclera to saponify and should be considered medical emergencies requiring immediate treatment. Abnormal coloring Redness of the sclera is typically caused by eye irritation causing blood vessels to expand, such as in conjunctivitis ("pink eye"). Episcleritis is a generally benign condition of the episclera causing eye redness. Scleritis is a serious inflammatory disease of the sclera causing redness of the sclera often progressing to purple. Yellowing or a light green color of the sclera is a visual symptom of jaundice. In cases of osteogenesis imperfecta, the sclera may appear to have a blue tint, more pronounced than the slight blue tint seen in children. The blue tint is caused by the showing of the underlying uveal tract (choroid and retinal pigment epithelium). In very rare but severe cases of kidney failure and liver failure, the sclera may turn black. See also Extraocular implant Scleral tattooing Sclerotomy Notes References External links Histology image: 08008loa – Histology Learning System at Boston University Atlas image: eye_1 at the University of Michigan Health System—"Sagittal Section Through the Eyeball" MedlinePlus Encyclopedia: 002295

Gephyrophobia

Gephyrophobia is the anxiety disorder or specific phobia characterized by the fear of bridges and tunnels. As a result, sufferers of gephyrophobia may avoid routes that will take them over bridges, or if they are a passenger, will act very apprehensively when passing over a bridge. The term gephyrophobia comes from the Greek γέφυρα (gephura), meaning "bridge", and φόβος (phobos), meaning "fear".Some possible manifestations of gephyrophobia may be fear of driving off the bridge, fear of a gust of wind blowing one off the bridge, or fear that the bridge will collapse when crossing it (e.g., fear that the bridge lacks structural integrity). The fear overlaps with acrophobia (the fear of heights) as gephyrophobia tends to be exacerbated in taller bridges as compared to those closer to the water or ground beneath. Dr. Michael Liebowitz, founder of the Anxiety Disorders Clinic at the New York State Psychiatric Institute, says, "Its not an isolated phobia, but usually part of a larger constellation ... Its people who get panic attacks. You get light-headed, dizzy; your heart races. You become afraid that youll feel trapped." It is a situational phobia.As of 2008, the New York State Thruway Authority would lead gephyrophobiacs over the Tappan Zee Bridge. A driver could call the authority in advance and arrange for someone to drive their car over the bridge for them. The authority performed the service about six times a year.The Maryland Transportation Authority previously offered a similar service for crossing the Chesapeake Bay Bridge, but that role is now filled by private companies.The Mackinac Bridge Authority, which oversees the Mackinac Bridge connecting Michigans Upper and Lower peninsulas, will drive needy gephyrophobiacs cars across the bridge for a nominal fee. Some one thousand drivers take advantage of this program annually. Leslie Ann Pluhar had her Yugo blown off the bridge in 1989. Later investigation concluded she had stopped her car over the open steel grating on the bridges span and that a gust of wind blowing through the grating pushed her vehicle off the bridge, but this assertion is not supported by recorded wind speed measurements taken on and around the bridge at the time of the accident. In media Gephyrophobia is the main plot in "The Bridge" episode of The Middle. The character Brick is plagued by the phobia. In 1965s A Charlie Brown Christmas, Lucy references gephyrophobia (albeit with a slight mispronunciation) when attempting to diagnose Charlie Browns problems at her psychiatric help stand. See also Galloping Gertie List of bridge disasters List of structural failures and collapses List of phobias == References ==

Coronary artery bypass surgery

Coronary artery bypass surgery, also known as coronary artery bypass graft (CABG, pronounced "cabbage") is a surgical procedure to treat coronary artery disease (CAD), the buildup of plaques in the arteries of the heart. It can relieve chest pain caused by CAD, slow the progression of CAD, and increase life expectancy. It aims to bypass narrowings in heart arteries by using arteries or veins harvested from other parts of the body, thus restoring adequate blood supply to the previously ischemic (deprived of blood) heart. There are two main approaches. The first uses a cardiopulmonary bypass machine, a machine which takes over the functions of the heart and lungs during surgery by circulating blood and oxygen. With the heart in arrest, harvested arteries and veins are used to connect across problematic regions—a construction known as surgical anastomosis. In the second approach, called the off-pump coronary artery bypass graft (OPCABG), these anastomoses are constructed while the heart is still beating. The anastomosis supplying the left anterior descending branch is the most significant one and usually, the left internal mammary artery is harvested for use. Other commonly employed sources are the right internal mammary artery, the radial artery, and the great saphenous vein. Doctors were searching for an effective way to treat chest pain (specifically, angina, a common symptom of CAD) since the beginning of the 20th century. In the 1960s, CABG was introduced in its modern form and has since become the main treatment for significant CAD. Significant complications of the operation include bleeding, heart problems (heart attack, arrhythmias), stroke, infections (often pneumonia) and injury to the kidneys. Uses Coronary artery bypass surgery aims to prevent death from coronary artery disease and improve quality of life by relieving angina. Indications for surgery are based on studies examining the pros and cons of CABG in various subgroups of patients (depending on the anatomy of the lesions or how well heart is functioning) with CAD and comparing it with other therapeutic strategies, most importantly percutaneous coronary intervention (PCI). Coronary artery disease Coronary artery disease is caused when coronary arteries of the heart accumulate atheromatic plaques, causing stenosis in one or more arteries and place myocardium at risk of myocardial infarction. CAD can occurs in any of the major vessels of coronary circulation, which are Left Main Stem, Left Ascending Artery, Circumflex artery, and Right Coronary Artery and their branches. CAD can be asymptomatic for some time- causing no trouble, can produce chest pain when patient is exercising, or can produce angina even at rest. The former is called stable angina, while the latter unstable angina. Worse, it can manifest as a myocardial infarction, in (which the blood flow to a part of myocardium is blocked. If the blood flow is not restored within a few hours, either spontaneously or by medical intervention, the specific part of the myocardium becomes necrotic (dies) and is replaced by a scar. It might even lead to other complications such as arrhythmias, rupture of the papillary muscles of the heart, or sudden death.Medical community has various modalities to detect CAD and examine its extent. Apart from history and clinical examination, noninvasive methods include Electrocardiography (ECG) (at rest or during exercise) and chest X-ray. Echocardiography can provide useful information on the functioning of myocardium, as the enlargement of Left Ventricle, the Ejection Fraction and the situation of heart valves. The best modalities to accurately detect CAD though are the coronary angiogram and the Coronary CT angiography. Angiogram can provide detailed anatomy of coronary circulation and lesions albeit not perfect. Significance of each lesions is determined by the diameter loss. Diameter loss of 50% translates to a 75% cross-sectional area loss which is considered moderate, by most groups. Severe stenosis is considered when the diameter loss is 2/3 of original diameter or more, that is 90% loss of cross-sectional area loss or more. To determine the severity of stenosis more accurately, interventional cardiologists might also employ Intravascular ultrasound. Intravascular ultrasound utilizes ultrasound technology to determine the severity of stenosis and provide information on the composition of the atheromatic plaque. Fractional flow reserve also can be of use. With FFR, the post-stenotic pressure is compared to mean aortic pressure. If the value is <0,80, then the stenosis is deemed significant. Indications for CABG Stable patients People suffering from angina during exercise are usually first treated with medical therapy. Noninvasive tests (as stress test, nuclear imaging, dobutamine stress echocardiography) help estimate which patients might benefit from undergoing coronary angiography. Many factors are taken into account but generally, people whose tests reviled that portions of cardiac wall receive less blood that normally should proceed with coronary angiography. There, lesions are identified and a decision is taken whether patient should undergo PCI or GABG.Generally, CABG is preferred over PCI when there is significant atheromatic burden on the coronaries, that is extensive and complex. According to current literature, decreased LV function, LM disease, complex triple system disease (including LAD, Cx and RCA) especially when the lesion at LAD is at its proximal part and diabetes, are factors that point patients will benefit more from CABG rather than PCI. Acute coronary syndrome During an acute heart event, named acute coronary syndrome, it is of vital importance to restore blood flow to the myocardium as fast as possible. Typically, patients arrive at hospital with chest pain. Initially they are treated with medical drugs, particularly the strongest drugs that prevent clots within vessels (dual antiplatelet therapy: aspirin and a P2Y12 inhibitor-like clopidogrel). Patients at risk of ongoing ischemia, undergo PCI and restore blood flow and thus oxygen delivery to the struggling myocardium. In cases where PCI failed to restore blood flow because of anatomic considerations or other technical problems, urgent CABG is indicated to save myocardium. It has also been noted that the timing of the operation, plays a role in survival, it is preferable to delay the surgery if possible (6 hours in cases of nontransmural MI, 3 days in cases of transmural MI)CABG of coronary lesions is also indicated in mechanical complications of an infarction (ventricular septal defect, papillary muscle rupture or myocardial rupture) should be addressed There are no absolute contraindications of CABG but severe disease of other organs such as liver or brain, limited life expectancy, fragility should be taken into consideration when planning the treatment path of a patient. Other cardiac surgery CABG is also performed when a patient is to undergo another cardiac surgical procedure, most commonly for valve disease, and at angiography a significant lesion of the coronaries is found. CABG can be employed in other situations other than atheromatic disease of native heart arteries, like for the dissection of coronary arteries (where a rupture of the coronary layers creates a pseudo-lumen and diminishes blood delivery to the heart) caused e.g. by pregnancy, tissue diseases as Enhler-Danlos, Marfan Syndrome, cocaine abuse or Percutaneous Coronary Intervention). A coronary aneurysm is another reason for CABG, for a thrombus might develop within the vessel, and possibly travel further. CABG vs PCI CABG and percutaneous coronary intervention (PCI) are the two modalities the medical community has to revascularize stenotic lesions of the cardiac arteries. Which one is preferable for each patient is still a matter of debate, but it is clear that in the presence of complex lesions, significant Left Main Disease and in diabetic patients, CABG seems to offer better results to patients than PCI. Strong indications for CABG also include symptomatic patients and in cases where LV function is impaired., CABG offers better results that PCI in left main disease and in multivessel CAD, because of the protection arterial conduits offer to the native arteries of the heart, by producing vasodilator factors and preventing advancement of atherotic plaques. The question which modality has been studied in various trials. Patients with unprotected LM Disease (runoff of LM is not protected by a patent graft since previous CABG operation) were studied in NOBLE and EXCEL trials. NOBLE, which was published in 2016 is a multi-European country that found that CABG outperforms PCI in the long run (5 years). EXCEL, also published in 2016, found that PCI has similar results to CABG at 3 years, but this similarity fades at 4th year and later (CABG is better to PCI).Diabetic patients were studied in the FREEDOM trial, first published in 2012 and a follow up. It demonstrated a significant advantage in this group of patients when treated with CABG (vs PCI). The superiority was evident in a 3.8 year follow up and, an even further followup at 7.5 years, of the same patients documented again the superiority of CABG, enphasazing the benefits in smokers and younger patients. BEST trial was published in 2015, comparing CABG and the latest technological advancement of PCI, second generation Drug-eluting stents in multivessel disease. Their results were indicative of CABG being a better option for patients with CAD. A trial published in 2021 (Fractional Flow Reserve versus Angiography for Multivessel Evaluation, FAME 3), also concluded that CABG is a safer option than PCI, when comparing results after one year from intervention. Complications The most common complications of CABG are postoperative bleeding, heart failure, Atrial fibrillation (a form of arrhythmia), stroke, renal dysfunction, and sternal wound infections.Postoperative bleeding occurs in 2-5% of cases and might force the cardiac team to take the patient back to operating theatre to control the bleeding The most common criterion for that is the amount blood drained by chest tubes, left after the operation. Re-operation addresses surgical causes of that bleeding, which might originate from the aorta, the anastomosis or a branch of the conduit insufficiently sealed or from the sternum. Medical causes of bleeding include platelet abnormalities or coagulopathy due to bypass or the rebound heparin effect (heparin administered at the beginning of CPB reappears at blood after its neutralization by protamine).As for heart failure, low cardiac output syndrome (LCOS) can occur up to 14% of CABG cases and is according to its severity, is treated with inotropes, IABP, optimization of pre- and afterload, or correction of blood gauzes and electrolytes. The aim is to keep a systolic blood pressure above 90mmHg and cardiac index (CI) more than 2.2 L/min/m2. LCOS is often transient. Postoperative Myocardial infarction can occur because of either technical or patients factors- its incidence is hard to estimate though due to various definitions, but most studies place it between 2 and 10%. New ECG features as Q waves and/or US documented alternation of cardiac wall motions are indicative. Ongoing ischemia might prompt emergency angiography or re-operation. Arrhythmias can also occur, most commonly atrial fibrillation (20-40%) that is treated with correcting electrolyte balance, rate and rhythm control.Various neurological adverse effects can occur after CABG, with total incidence about 1,5% they can manifest as type 1-focal deficits (such as stroke or coma) or type 2- global ones (such as delirium). Inflammation caused by CPB, hypoperfusion or cerebral embolism. Cognitive impairment has been reported in up to 80% cases after CABG at discharge and lasting up to 40% for a year. The causes are rather unclear, it seems CPB is not a suspect since even in CABG cases not including CPB (as in Off-Pump CABG), the incidence is the same, whilst PCI has the same incidence of cognitive decline as well.Infections are also a problem of the postoperative period. Sternal would infections (superficial or deep), most commonly caused by Staphylococcus aureus, can add to mortality. Harvesting of two mammary arteries is a risk factor since the perfusion of sternum is significantly impaired. Pneumonia can also occur. Complications from the GI track have been described, most commonly are caused by peri-operative medications. Procedure Preoperative workup and strategy Routine preoperative workup aims to check the baseline status of systems and organs other than heart. Thus a chest x-ray to check lungs, complete blood count, renal and liver function tests are done to screen for abnormalities. Physical examination to determine the quality of the grafts or the safety of removing them, such as varicosities in the legs, or the Allen test in the arm is performed to be sure that blood supply to the arm wont be disturbed critically.Administration of anticoagulants such as aspirin, clopidogrel, ticagrelol and others, is stopped serval days before the operation, to prevent excessive bleeding during the operation and in the following period. Warfarin is also stopped for the same reason and the patient starts being administered heparin products after INR falls below 2.0.After the angiogram is reviewed by the surgical team, targets are selected (that is, which native arteries will be bypassed and where the anastomosis should be placed). Ideally, all major lesions in significant vessels should be addressed. Most commonly, left internal thoracic artery (LITA; formerly, left internal mammary artery, LIMA) is anastomosed to left anterior descending artery (LAD) because the LAD is the most significant artery of the heart, since it supplies a larger portion of myocardium than other arteries.A conduit can be used to graft one or more native arteries. In the latter case, an end-to-side anastomosis is performed. In the former, utilizing a sequential anastomosis, a graft can then deliver blood to two or more native vessels of the heart. Also, the proximal part of a conduit can be anastomosed to the side of another conduit (by a Y or a T anastomose) adding to the versality of options for the architecture of CABG. It is preferred not to harvest too much length of conduits since it might cause some patients to need re-operation. With CBP (on-pump) The patient is brought to the operating theatre, intubated and lines (e.g., peripheral IV cannulae; central lines such as internal jugular cannulae) are inserted for drug administration and monitoring. The traditional way of a CABG follows: HarvestingA sternotomy is made, while conduits are being harvested (either from the arm or the leg). Then LITA (formerly, LIMA) is harvested through the sternotomy. There are two common ways of mobilizing the LITA, the pedicle (i.e., a pedicle consisting of the artery plus surrounding fat and veins) and the skeletonized (i.e., freed of other tissues). Before being divided in its more distal part, heparin is administered to the patient via a peripheral line (for clot prevention). Catheterization and establishment of cardiopulmonary bypass (on-pump)After harvesting, the pericardium is opened and stay sutures are placed to keep it open. Purse string sutures are placed in aorta to prepare the insertions of the aortic cannula and the catheter for cardioplegia (a solution high in potassium that serves to arrest the heart). Another purse string is placed in right atrium for the venous cannula. Then the cannulas and the catheter are placed, cardiopulmonary bypass is commenced (venous deoxygenated blood arriving to the heart is forwarded to the CBP machine to get oxygenated and delivered to aorta to keep rest of the body saturated, and often cooled to 32 - 34 degrees celsius in order to slow down the metabolism and minimize as much as possible the demand for oxygen. A clamp is placed on the Aorta between the cardioplegic catheter and aortic cannula, so the cardioplegic solution that the flow is controlled by the surgeon that clamps Aorta. Within minutes, heart stops beating. Anastomosis (grafting)With the heart still, the tip of the heart is taken out of pericardium, so the native arteries lying in the posterior side of the heart are accessible. Usually, distal anastomosis are constructed first (first to right coronary system, then to the circumflex) and then the sequential anastomosis if necessary. Surgeons check the anastomosis for patency or leaking and if everything is as it should be, surgeons insert the graft within the pericardium, sometimes attached to the cardioplegic catheter. The anastomosis of LIMA to LAD is usually the last one of the distal anastomoses to be constructed, while it is being constructed the rewarming process starts (by the CPB).. After the anastomosis is completed and checked for leaks, the proximal anastomoses of the conduits, if any, are next. They can be done either with the clamp still on or after removing the aortic clamp and isolating a small segment of the aorta by placing a partial clamp (but atheromatic aortas might be damaged by overhandling them; atheromatic derbis might get detached and cause embolization in end organs) Weaning from cardiopulmonary bypass and closureAfter the proximal anastomoses are done, the clamp is removed, aorta and conduits deaired, pacing wires might be placed if indicated and if the heart and other systems are functioning well CBP is discontinued, cannulas removed and protamine is administered to reverse the effect of heparin. After possible bleeding sites are checked, chest tubes are placed and sternum is closed. Off-pump (OPCABG) Off-pump coronary artery bypass graft (OPCABG) surgery avoids using CPB machine by stabilizing small segments of the heart. It takes great care and coordination among the surgical team and anesthesiologists to not manipulate the heart too much so hemodynamic stability will not be compromised; however, if it is compromised, it should be detected immediately and appropriate action should be taken. To keep heart beating effectively, some maneuvers can take place like placing atrial wires to protect from bradycardia, placing stitches or incisions to pericardium to help exposure. Snares and tapes are used to facilitate exposure. the aim is to avoid distal ischemia by occluding the vessel supplying distal portions of the left ventricle, so usually LIMA to LAD is the first to be anastomosed and others follow. For the anastomosis, a fine tube blowing humidified CO2 is used to keep the surgical field clean of blood. Also, a shunt might be used so the blood can travel pass the anastomotic site. After the distal anastomosis are completed, proximal anastomosis to the aorta are constructed with a partially aortic clamp and rest is similar with on-pump CABG. Alternative approaches and special situations When CABG is performed as an emergency because of hemodynamic compromise after an infraction, priority is to salvage the struggling myocardium. Pre-operatively, an intra-aortic balloon pump (IABP) might be inserted to relieve some of the burden of pumping blood, effectively reducing the amount of oxygen needed by myocardium. Operatively, the standard practice is to place the patient on CPB as soon as possible and revascularize the heart with three saphenous veins. Calcified aorta also poses a problem since it is very dangerous to clamp. In this case, the operation can be done as off-pump CAB utilizing both IMAs or Y, T and sequential grafts, or in deep hypothermic arrest, that is lower the temperature of the body to little above 20 Celsius, can also force the heart stop moving. In cases were a significant artery is totally occluded, theres a possibility to remove the atheroma, and using the same hole in the artery to perform an anastomosis ·this technique is called endarterectomy and is usually performed at the Right Coronary System.Reoperations of CABG (another CABG operation after a previous one), poses some difficulties: Heart may be too close to the sternum and thus at risk when cutting the sternum again, so an oscillating saw is used. Heart may be covered with strong adhesions to adjusting structures, adding to the difficulty of the procedure. Also, aging grafts pose a dilemma, whether they should be replaced with new ones or not. Manipulation of vein grafts risks dislodgement of atheromatic debris and is avoided."Minimally Invasive revascularization" (commonly MIDCAB form minimally invasive direct coronary artery bypass) is a technique that strives to avoid a large sternotomy. It utilizes off pump techniques to place a graft, usually LIMA at LAD. LIMA is monilized through a left thoracotomy, or even endoscopically through a thoracoscope placed in the left chest. Robotic Coronary revascularization avoids the sternotomy to prevent infections and bleeding. Both conduit harvesting and the anastomosis are performed with the aid of a robot, through a thoracotomy. There is still no widespread use of the technique though. Usually it is combined with Hybrid Coronary Revascularization, which is the strategy where combined methods of CABG and PCI are employed. LIMA to LAD is performed in the operating theatre and other lesions are treated with PCI, either at the operating room, right after the anastomosis or serval days later. After the procedure After the procedure, the patient is usually transferred to the intensive care unit, where they are extubated if it hasnt been done already in the operating theatre. The following day they exit the ICU, and 4 days later, if no complications occur, the patient is discharged from the hospital.A series of drugs are commonly used in the early postoperative period. Dobutamine, a beta agent, can be used to increase the cardiac output that sometimes occurs some hours after the operation. Beta blockers are used to prevent atrial fibrillation and other supraventricular arrhythmias. Biatrial pacing through the pacing wires inserted at operation might help towards preventing atrial fibrillation. Aspirin 80mg is used to prevent graft failure. Angiotensin-converting enzyme (ACE) inhibitors and Angiotensin receptor blockers (ARBs) are used to control blood pressure, especially in patients with low cardiac function (<40%). Amlodipine, a calcium channel blocker, is used for patients that radial artery was used as a graft.After the discharge, patients might suffer from insomnia, low appetite, decreased sex drive, and memory problems. This effect is usually transient and lasts 6 to 8 weeks. A tailored exercise plan usually benefits the patient. Results CABG is the best procedure to reduce mortality from severe CAD and improve quality of life. Operative mortality relates strongly to age of patient. According to a study by Eagle et al, for patients 50-59 years old theres an operative mortality rate of 1.8% while patients older than 80, the risk is 8.3%. Other factors which increase mortality are: female gender, re-operation, dysfunction of Left ventricle and left main disease. In most cases, CABG relieves angina, but in some patients it reoccurs in a later stage of their lives. Around 60% of patient will be angina free, 10 years after their operation. Myocardial infarction is rare 5 years after a CABG, but its prevalence increases with time. Also, the risk of sudden death is low for CABG patients. Quality of life is also high for at least 5 years, then starts to decline.The beneficial effects of CABG are clear at cardiac level. LV function is improved and malfunctioning segments of the heart (dyskinetic-moving inefficiently or even akinetic-not moving) can show signs of improvement. Both systolic and diastolic functions are improved and keep improving for up to 5 years in some cases. LV function, and myocardial perfusion, during exercise also improves after CABG. But when the LV function is severely impaired before operation (EF<30%), the benefits at the heart are less impressive in terms of segmental wall movement, but still significant since other parameters might improve as LV functions improves, the pulmonary hypertension might be relieved and survival is prolonged.It is hard to determine the total risk of the procedure since the group of patients undergoing CABG is a heterogeneous one, hence various subgroups have different risk, but it seems like the results for younger patients are better. Also, a CABG with two rather one internal mammary arteries seems to offer greater protection from CAD but results are not yet conclusive. Grafts Various conduits can be utilized for CABG- they fall into two main categories, arteries and veins. Arteries have a superior long term patency, but veins are still largely in use due to practicality. Arterial grafts that can be used originate from the part of the Internal Mammary Artery (IMA) that runs near the edge of sternum and can easily be mobilized and anastomosed to the native target vessel of the heart. Left is most often used as it is closer to heart but Right IMA is utilized depending on patient and surgeon preferences. ITAs advantages are mostly due to their endothelial cells that produce factors (Endothelium-derived relaxing factor and prostacyclin) that protect the artery from atherosclerosis and thus stenosis or occlusion. But using two ITAs has drawbacks, high rate of specific complications (deep sternal wound infections) in some subgroups of patients, mainly in obese and diabetic ones. Left radial artery and left Gastroepiploic artery can be used as well. Long term patency is influenced by the type of artery used, as well as intrinsic factors of the cardiac arterial circulation.Venous grafts used are mostly great saphenous veins and in some cases lesser saphenous vein. Their patency rate is lower than arteries. Aspirin protects grafts from occlusion; adding clopidogrel does not improve rates. CABG vs PCI CABG and percutaneous coronary intervention (PCI) are the two modalities the medical community has to revascularize stenotic lesions of the cardiac arteries. Which one is preferable for each patient is still a matter of debate, but it is clear that in the presence of complex lesions, significant Left Main Disease and in diabetic patients, CABG seems to offer better results to patients than PCI. Strong indications for CABG also include symptomatic patients and in cases where LV function is impaired. History Pre-CABG Surgical interventions aiming relieve angina and prevent death in the early 20th century, were either sympatheticectomy (a cut on the sympathetic chain that supplies the heart, with disappointing and inconsistent results) or pericardial abrasion (with the hope that adhesions would create significant collateral circulation).French Surgeon Alexis Carrel was the first to anastomose a vessel (a branch of carotid artery) to a native artery in the Heart, in a canine model- but because of technical difficulties the operation could not be reproduced. In mid 20th century, revascularization efforts continued. Beck CS, used a carotid conduit to connect descending aorta to coronary sinus -the biggest vein of the heart, while Arthur Vineberg used skeletonized LIMA, placing it in a small tunnel he created next to LAD (known "Vineberg Procedure"), with the hope of spontaneous collateral circulation would form, and it did in canine experiments but was not successful in humans. Goetz RH was the first to perform an anastomosis of the IMA to LAD in the 1960 utilizing a sutureless technique.The development of coronary angiography in 1962 by Mason Sones, helped medical doctors to identify both patients that are in need of operation, but also which native heart vessels should be bypassed. In 1964, Soviet cardiac

Coronary artery bypass surgery

surgeon, Vasilii Kolesov, performed the first successful internal mammary artery–coronary artery anastomosis, followed by Michael DeBakey in the USA. But it was René Favaloro that standarized the procedure. Their advances made CABG as the standard of care of CAD patients. The CABG era The "modern" era of the CABG begun in 1964 when the Soviet cardiac surgeon Vasilii Kolesov performed the first successful internal mammary artery–coronary artery anastomosis in 1964, while Michael DeBakey used a saphenous vein to create an aorta-coronary artery bypass. The Argentinean surgeon Rene Favaloro advanced and standardized the CABG technique using the patients saphenous vein.Introduction of cardioplegia led to CABG becoming a much less risky operation. A major obstacle of CABG during those times were ischemia and infarction, occurring while the heart was stopped to allow surgeons to construct the distal anastomosis. In the 1970s potassium cardioplegia was utilized. Cardioplegia minimized the oxygen demands of the heart, thus the effects of ischemia were also minimized. Refinement of cardioplegia in the 1980s made CABG less risky (lowering perioperative mortality) and thus a more attractive option when dealing with CAD.In the late 1960s, after the work of Rene Favaloro, the operation was still performed in a few centers of excellence, but was anticipated to change the landscape of Coronary Artery Disease, a significant killer in the developed world. More and more centers began performing CABG, resulting in 114,000 procedures/year in the USA by 1979. The introduction of PCI did not lead to the abandonment of CABG; the number of both procedures continued to increase, albeit PCIs grew more rapidly. In the following decades CABG was extensively studied and compared to PCI. The absence of a clear advantage of CABG over PCI led to a small decrease in numbers of CABGs in some countries (like the USA) at the turn of the millennium, but in European countries CABG was increasingly performed (mainly in Germany). Research is still ongoing on CABG vs PCI.In the history of graft selection, again the work of Favaloro was fundamental. He established that the use of bilateral IMAs was superior to vein grafts. The following years, surgeons examined the use of other arterial grafts (splenic, gastroepiploic mesenteric, subscapular and others) but none of these matched the patency rates of IMA. Carpentier in 1971 introduced the us of the radial artery, which was initially prone to failure, but the evolution of harvesting techniques in the next two decades improved patency significantly. See also Angioplasty Cardiothoracic surgery Cleveland Clinic Dresslers syndrome Hybrid coronary revascularization Totally endoscopic coronary artery bypass surgery Chest tube References Sources Al-Atassi, Talal; Toeg, Hadi D.; Chan, Vincent; Ruel, Marc (2016). "Coronary Artery Bypass Grafting". In Frank Sellke; Pedro J. del Nido (eds.). Sabiston and Spencer Surgery of the Chest. ISBN 978-0-323-24126-7. Bojar, R.M. (2021). Manual of Perioperative Care in Adult Cardiac Surgery. Wiley. ISBN 978-1-119-58255-7. Retrieved 2022-10-26. Farina, Piero; Gaudino, Mario Fulvio Luigi; Taggart, David Paul (2020). "The Eternal Debate With a Consistent Answer: CABG vs PCI". Seminars in Thoracic and Cardiovascular Surgery. Elsevier BV. 32 (1): 14–20. doi:10.1053/j.semtcvs.2019.08.009. ISSN 1043-0679. S2CID 201632303. Fearon, William F.; Zimmermann, Frederik M.; De Bruyne, Bernard; Piroth, Zsolt; van Straten, Albert H.M.; Szekely, Laszlo; Davidavičius, Giedrius; Kalinauskas, Gintaras; Mansour, Samer; Kharbanda, Rajesh; Östlund-Papadogeorgos, Nikolaos; Aminian, Adel; Oldroyd, Keith G.; Al-Attar, Nawwar; Jagic, Nikola; Dambrink, Jan-Henk E.; Kala, Petr; Angerås, Oskar; MacCarthy, Philip; Wendler, Olaf; Casselman, Filip; Witt, Nils; Mavromatis, Kreton; Miner, Steven E.S.; Sarma, Jaydeep; Engstrøm, Thomas; Christiansen, Evald H.; Tonino, Pim A.L.; Reardon, Michael J.; Lu, Di; Ding, Victoria Y.; Kobayashi, Yuhei; Hlatky, Mark A.; Mahaffey, Kenneth W.; Desai, Manisha; Woo, Y. Joseph; Yeung, Alan C.; Pijls, Nico H.J. (2022-01-13). "Fractional Flow Reserve–Guided PCI as Compared with Coronary Bypass Surgery". New England Journal of Medicine. Massachusetts Medical Society. 386 (2): 128–137. doi:10.1056/nejmoa2112299. ISSN 0028-4793. PMID 34735046. S2CID 242940936. Head, S. J.; Kieser, T. M.; Falk, V.; Huysmans, H. A.; Kappetein, A. P. (2013-10-01). "Coronary artery bypass grafting: Part 1--the evolution over the first 50 years". European Heart Journal. Oxford University Press (OUP). 34 (37): 2862–2872. doi:10.1093/eurheartj/eht330. ISSN 0195-668X. PMID 24086085. Smith, Peter K.; Schroder, Jacob N. (2016). "On-Pump Coronary Artery Bypass Grafting". In Josef E. Fischer (ed.). Master Techniques in Surgery CARDIAC SURGERY. ISBN 9781451193534. Kouchoukos, Nicholas; Blackstone, E. H.; Hanley, F. L.; Kirklin, J. K. (2013). Kirklin/Barratt-Boyes Cardiac Surgery E-Book (4th ed.). Elsevier. ISBN 978-1-4160-6391-9. Mick, Stephanie; Keshavamurthy, Suresh; Mihaljevicl, Tomislav; Bonatti, Johannes (2016). "Robotic and Alternative Approaches to Coronary Artery Bypass Grafting". In Frank Sellke; Pedro J. del Nido (eds.). Sabiston and Spencer Surgery of the Chest. pp. 1603–1615. ISBN 978-0-323-24126-7. Ngu, Janet M. C.; Sun, Louise Y.; Ruel, Marc (2018). "Pivotal contemporary trials of percutaneous coronary intervention vs. coronary artery bypass grafting: a surgical perspective". Annals of Cardiothoracic Surgery. AME Publishing Company. 7 (4): 527–532. doi:10.21037/acs.2018.05.12. ISSN 2225-319X. PMC 6082775. PMID 30094218. Welt, Frederick G.P. (2022-01-13). "CABG versus PCI — End of the Debate?". New England Journal of Medicine. Massachusetts Medical Society. 386 (2): 185–187. doi:10.1056/nejme2117325. ISSN 0028-4793. PMID 35020989. External links Lawton JS, Tamis-Holland JE, Bangalore S, Bates ER, Beckie TM, Bischoff JM, Bittl JA, Cohen MG, DiMaio JM, Don CW, Fremes SE, Gaudino MF, Goldberger ZD, Grant MC, Jaswal JB, Kurlansky PA, Mehran R, Metkus TS Jr, Nnacheta LC, Rao SV, Sellke FW, Sharma G, Yong CM, Zwischenberger BA. 2021 ACC/AHA/SCAI guideline for coronary artery revascularization: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. J Am Coll Cardiol. 2022;79:e21-e129

Unemployment

Unemployment, according to the OECD (Organisation for Economic Co-operation and Development), is people above a specified age (usually 15) not being in paid employment or self-employment but currently available for work during the reference period.Unemployment is measured by the unemployment rate, which is the number of people who are unemployed as a percentage of the labour force (the total number of people employed added to those unemployed).Unemployment can have many sources, such as the following: new technologies and inventions the status of the economy, which can be influenced by a recession competition caused by globalization and international trade policies of the government regulation and marketUnemployment and the status of the economy can be influenced by a country through, for example, fiscal policy. Furthermore, the monetary authority of a country, such as the central bank, can influence the availability and cost for money through its monetary policy. In addition to theories of unemployment, a few categorisations of unemployment are used for more precisely modelling the effects of unemployment within the economic system. Some of the main types of unemployment include structural unemployment, frictional unemployment, cyclical unemployment, involuntary unemployment and classical unemployment. Structural unemployment focuses on foundational problems in the economy and inefficiencies inherent in labor markets, including a mismatch between the supply and demand of laborers with necessary skill sets. Structural arguments emphasize causes and solutions related to disruptive technologies and globalization. Discussions of frictional unemployment focus on voluntary decisions to work based on individuals valuation of their own work and how that compares to current wage rates added to the time and effort required to find a job. Causes and solutions for frictional unemployment often address job entry threshold and wage rates. According to the UNs International Labour Organization (ILO), there were 172 million people worldwide (or 5% of the reported global workforce) without work in 2018.Because of the difficulty in measuring the unemployment rate by, for example, using surveys (as in the United States) or through registered unemployed citizens (as in some European countries), statistical figures such as the employment-to-population ratio might be more suitable for evaluating the status of the workforce and the economy if they were based on people who are registered, for example, as taxpayers. Definitions, types, and theories The state of being without any work yet looking for work is called unemployment. Economists distinguish between various overlapping types of and theories of unemployment, including cyclical or Keynesian unemployment, frictional unemployment, structural unemployment and classical unemployment. Some additional types of unemployment that are occasionally mentioned are seasonal unemployment, hardcore unemployment, and hidden unemployment. Though there have been several definitions of "voluntary" and "involuntary unemployment" in the economics literature, a simple distinction is often applied. Voluntary unemployment is attributed to the individuals decisions, but involuntary unemployment exists because of the socio-economic environment (including the market structure, government intervention, and the level of aggregate demand) in which individuals operate. In these terms, much or most of frictional unemployment is voluntary since it reflects individual search behavior. Voluntary unemployment includes workers who reject low-wage jobs, but involuntary unemployment includes workers fired because of an economic crisis, industrial decline, company bankruptcy, or organizational restructuring. On the other hand, cyclical unemployment, structural unemployment, and classical unemployment are largely involuntary in nature. However, the existence of structural unemployment may reflect choices made by the unemployed in the past, and classical (natural) unemployment may result from the legislative and economic choices made by labour unions or political parties. The clearest cases of involuntary unemployment are those with fewer job vacancies than unemployed workers even when wages are allowed to adjust and so even if all vacancies were to be filled, some unemployed workers would still remain. That happens with cyclical unemployment, as macroeconomic forces cause microeconomic unemployment, which can boomerang back and exacerbate those macroeconomic forces. Real wage unemployment Classical, natural, or real-wage unemployment, occurs when real wages for a job are set above the market-clearing level, causing the number of job-seekers to exceed the number of vacancies. On the other hand, most economists argue that as wages fall below a livable wage, many choose to drop out of the labour market and no longer seek employment. That is especially true in countries in which low-income families are supported through public welfare systems. In such cases, wages would have to be high enough to motivate people to choose employment over what they receive through public welfare. Wages below a livable wage are likely to result in lower labor market participation in the above-stated scenario. In addition, consumption of goods and services is the primary driver of increased demand for labor. Higher wages lead to workers having more income available to consume goods and services. Therefore, higher wages increase general consumption and as a result demand for labor increases and unemployment decreases. Many economists have argued that unemployment increases with increased governmental regulation. For example, minimum wage laws raise the cost of some low-skill laborers above market equilibrium, resulting in increased unemployment as people who wish to work at the going rate cannot (as the new and higher enforced wage is now greater than the value of their labour). Laws restricting layoffs may make businesses less likely to hire in the first place, as hiring becomes more risky.However, that argument overly simplifies the relationship between wage rates and unemployment by ignoring numerous factors that contribute to unemployment. Some, such as Murray Rothbard, suggest that even social taboos can prevent wages from falling to the market-clearing level.In Out of Work: Unemployment and Government in the Twentieth-Century America, economists Richard Vedder and Lowell Gallaway argue that the empirical record of wages rates, productivity, and unemployment in America validates classical unemployment theory. Their data shows a strong correlation between adjusted real wage and unemployment in the United States from 1900 to 1990. However, they maintain that their data does not take into account exogenous events. Cyclical unemployment Cyclical, deficient-demand, or Keynesian unemployment occurs when there is not enough aggregate demand in the economy to provide jobs for everyone who wants to work. Demand for most goods and services falls, less production is needed and consequently, fewer workers are needed, wages are sticky and do not fall to meet the equilibrium level, and unemployment results. Its name is derived from the frequent ups and downs in the business cycle, but unemployment can also be persistent, such as during the Great Depression. With cyclical unemployment, the number of unemployed workers exceeds the number of job vacancies and so even if all open jobs were filled, some workers would still remain unemployed. Some associate cyclical unemployment with frictional unemployment because the factors that cause the friction are partially caused by cyclical variables. For example, a surprise decrease in the money supply may suddenly inhibit aggregate demand and thus inhibit labor demand. Keynesian economists, on the other hand, see the lack of supply of jobs as potentially resolvable by government intervention. One suggested intervention involves deficit spending to boost employment and goods demand. Another intervention involves an expansionary monetary policy to increase the supply of money, which should reduce interest rates, which, in turn, should lead to an increase in non-governmental spending. Unemployment under "full employment" In demands based theory, it is possible to abolish cyclical unemployment by increasing the aggregate demand for products and workers. However, the economy eventually hits an "inflation barrier" that is imposed by the four other kinds of unemployment to the extent that they exist. Historical experience suggests that low unemployment affects inflation in the short term but not the long term. In the long term, the velocity of money supply measures such as the MZM ("money zero maturity", representing cash and equivalent demand deposits) velocity is far more predictive of inflation than low unemployment.Some demand theory economists see the inflation barrier as corresponding to the natural rate of unemployment. The "natural" rate of unemployment is defined as the rate of unemployment that exists when the labour market is in equilibrium, and there is pressure for neither rising inflation rates nor falling inflation rates. An alternative technical term for that rate is the NAIRU, the Non-Accelerating Inflation Rate of Unemployment. Whatever its name, demand theory holds that if the unemployment rate gets "too low," inflation will accelerate in the absence of wage and price controls (incomes policies). One of the major problems with the NAIRU theory is that no one knows exactly what the NAIRU is, and it clearly changes over time. The margin of error can be quite high relative to the actual unemployment rate, making it hard to use the NAIRU in policy-making.Another, normative, definition of full employment might be called the ideal unemployment rate. It would exclude all types of unemployment that represent forms of inefficiency. This type of "full employment" unemployment would correspond to only frictional unemployment (excluding that part encouraging the McJobs management strategy) and so would be very low. However, it would be impossible to attain this full-employment target using only demand-side Keynesian stimulus without getting below the NAIRU and causing accelerating inflation (absent incomes policies). Training programs aimed at fighting structural unemployment would help here. To the extent that hidden unemployment exists, it implies that official unemployment statistics provide a poor guide to what unemployment rate coincides with "full employment." Structural unemployment Structural unemployment occurs when a labour market is unable to provide jobs for everyone who wants one because there is a mismatch between the skills of the unemployed workers and the skills needed for the available jobs. Structural unemployment is hard to separate empirically from frictional unemployment except that it lasts longer. As with frictional unemployment, simple demand-side stimulus will not work to abolish this type of unemployment easily. Structural unemployment may also be encouraged to rise by persistent cyclical unemployment: if an economy suffers from longlasting low aggregate demand, it means that many of the unemployed become disheartened, and their skills (including job-searching skills) become "rusty" and obsolete. Problems with debt may lead to homelessness and a fall into the vicious circle of poverty. That means that they may not fit the job vacancies that are created when the economy recovers. The implication is that sustained high demand may lower structural unemployment. This theory of persistence in structural unemployment has been referred to as an example of path dependence or "hysteresis." Much technological unemployment, caused by the replacement of workers by machines might be counted as structural unemployment. Alternatively, technological unemployment might refer to the way in which steady increases in labour productivity mean that fewer workers are needed to produce the same level of output every year. The fact that aggregate demand can be raised to deal with the problem suggests that the problem is instead one of cyclical unemployment. As indicated by Okuns law, the demand side must grow sufficiently quickly to absorb not only the growing labour force but also the workers who are made redundant by the increased labour productivity. Seasonal unemployment may be seen as a kind of structural unemployment since it is linked to certain kinds of jobs (construction and migratory farm work). The most-cited official unemployment measures erase this kind of unemployment from the statistics using "seasonal adjustment" techniques. That results in substantial and permanent structural unemployment. Frictional unemployment Frictional unemployment is the time period between jobs in which a worker searches for or transitions from one job to another. It is sometimes called search unemployment and can be voluntary, based on the circumstances of the unemployed individual. Frictional unemployment exists because both jobs and workers are heterogeneous, and a mismatch can result between the characteristics of supply and demand. Such a mismatch can be related to skills, payment, work-time, location, seasonal industries, attitude, taste, and a multitude of other factors. New entrants (such as graduating students) and re-entrants (such as former homemakers) can also suffer a spell of frictional unemployment. Workers and employers accept a certain level of imperfection, risk or compromise, but usually not right away. They will invest some time and effort to find a better match. That is, in fact, beneficial to the economy since it results in a better allocation of resources. However, if the search takes too long and mismatches are too frequent, the economy suffers since some work will not get done. Therefore, governments will seek ways to reduce unnecessary frictional unemployment by multiple means including providing education, advice, training, and assistance such as daycare centers. The frictions in the labour market are sometimes illustrated graphically with a Beveridge curve, a downward-sloping, convex curve that shows a correlation between the unemployment rate on one axis and the vacancy rate on the other. Changes in the supply of or demand for labour cause movements along the curve. An increase or decrease in labour market frictions will shift the curve outwards or inwards. Hidden unemployment Official statistics often underestimate unemployment rates because of hidden, or covered, unemployment. That is the unemployment of potential workers that are not reflected in official unemployment statistics because of how the statistics are collected. In many countries, only those who have no work but are actively looking for work and/or qualifying for social security benefits are counted as unemployed. Those who have given up looking for work and sometimes those who are on government "retraining" programs are not officially counted among the unemployed even though they are not employed. The statistic also does not count the "underemployed", those working fewer hours than they would prefer or in a job that fails to make good use of their capabilities. In addition, those who are of working age but are currently in full-time education are usually not considered unemployed in government statistics. Traditional unemployed native societies who survive by gathering, hunting, herding, and farming in wilderness areas may or may not be counted in unemployment statistics. Long-term unemployment Long-term unemployment (LTU) is defined in European Union statistics as unemployment lasting for longer than one year (while unemployment lasting over two years is defined as very long-term unemployment). The United States Bureau of Labor Statistics (BLS), which reports current long-term unemployment rate at 1.9 percent, defines this as unemployment lasting 27 weeks or longer. Long-term unemployment is a component of structural unemployment, which results in long-term unemployment existing in every social group, industry, occupation, and all levels of education.In 2015 the European Commission published recommendations on how to reduce long-term unemployment. These advised governments to: encourage long-term unemployed people to register with an employment service; provide each registered long-term unemployed person with an individual in-depth assessment to identify their needs and potential within 18 months; offer a tailor-made job integration agreement (JIA) to all registered long-term unemployed within 18 months. These might include measures such as mentoring, help with job search, further education and training, support for housing, transport, child and care services and rehabilitation. Each person would have a single point of contact to access this support, which would be implemented in partnership with employers.In 2017–2019 it implemented the Long-Term Unemployment project to research solutions implemented by EU member states and produce a toolkit to guide government action. Progress was evaluated in 2019. Marxian theory of unemployment It is in the very nature of the capitalist mode of production to overwork some workers while keeping the rest as a reserve army of unemployed paupers. Marxists share the Keynesian viewpoint of the relationship between economic demand and employment, but with the caveat that the market systems propensity to slash wages and reduce labor participation on an enterprise level causes a requisite decrease in aggregate demand in the economy as a whole, causing crises of unemployment and periods of low economic activity before the capital accumulation (investment) phase of economic growth can continue. According to Karl Marx, unemployment is inherent within the unstable capitalist system and periodic crises of mass unemployment are to be expected. He theorized that unemployment was inevitable and even a necessary part of the capitalist system, with recovery and regrowth also part of the process. The function of the proletariat within the capitalist system is to provide a "reserve army of labour" that creates downward pressure on wages. This is accomplished by dividing the proletariat into surplus labour (employees) and under-employment (unemployed). This reserve army of labour fight among themselves for scarce jobs at lower and lower wages. At first glance, unemployment seems inefficient since unemployed workers do not increase profits, but unemployment is profitable within the global capitalist system because unemployment lowers wages which are costs from the perspective of the owners. From this perspective low wages benefit the system by reducing economic rents. Yet, it does not benefit workers; according to Karl Marx, the workers (proletariat) work to benefit the bourgeoisie through their production of capital. Capitalist systems unfairly manipulate the market for labour by perpetuating unemployment which lowers laborers demands for fair wages. Workers are pitted against one another at the service of increasing profits for owners. As a result of the capitalist mode of production, Marx argued that workers experienced alienation and estrangement through their economic identity. According to Marx, the only way to permanently eliminate unemployment would be to abolish capitalism and the system of forced competition for wages and then shift to a socialist or communist economic system. For contemporary Marxists, the existence of persistent unemployment is proof of the inability of capitalism to ensure full employment. Measurement There are also different ways national statistical agencies measure unemployment. The differences may limit the validity of international comparisons of unemployment data. To some degree, the differences remain despite national statistical agencies increasingly adopting the definition of unemployment of the International Labour Organization. To facilitate international comparisons, some organizations, such as the OECD, Eurostat, and International Labor Comparisons Program, adjust data on unemployment for comparability across countries. Though many people care about the number of unemployed individuals, economists typically focus on the unemployment rate, which corrects for the normal increase in the number of people employed caused by increases in population and increases in the labour force relative to the population. The unemployment rate is expressed as a percentage and calculated as follows: Unemployment rate = Unemployed workers Total labor force × 100 {\displaystyle {\text{Unemployment rate}}={\frac {\text{Unemployed workers}}{\text{Total labor force}}}\times 100} As defined by the International Labour Organization, "unemployed workers" are those who are currently not working but are willing and able to work for pay, currently available to work, and have actively searched for work. Individuals who are actively seeking job placement must make the effort to be in contact with an employer, have job interviews, contact job placement agencies, send out resumes, submit applications, respond to advertisements, or some other means of active job searching within the prior four weeks. Simply looking at advertisements and not responding will not count as actively seeking job placement. Since not all unemployment may be "open" and counted by government agencies, official statistics on unemployment may not be accurate. In the United States, for example, the unemployment rate does not take into consideration those individuals who are not actively looking for employment, such as those who are still attending college.According to the OECD, Eurostat, and the US Bureau of Labor Statistics the unemployment rate is the number of unemployed people as a percentage of the labour force. "An unemployed person is defined by Eurostat, according to the guidelines of the International Labour Organization, as: someone aged 15 to 74 (in Italy, Spain, the United Kingdom, Iceland, Norway: 16 to 74 years); without work during the reference week; available to start work within the next two weeks (or has already found a job to start within the next three months); actively having sought employment at some time during the last four weeks."The labour force, or workforce, includes both employed (employees and self-employed) and unemployed people but not the economically inactive, such as pre-school children, school children, students and pensioners.The unemployment rate of an individual country is usually calculated and reported on a monthly, quarterly, and yearly basis by the National Agency of Statistics. Organisations like the OECD report statistics for all of its member states.Certain countries provide unemployment compensation for a certain period of time for unemployed citizens who are registered as unemployed at the government employment agency. Furthermore, pension receivables or claims could depend on the registration at the government employment agency.In many countries like in Germany, the unemployment rate is based on the number of people who are registered as unemployed. Other countries like the United States use a labour force survey to calculate the unemployment rate.The ILO describes four different methods to calculate the unemployment rate: Labour Force Sample Surveys are the most preferred method of unemployment rate calculation since they give the most comprehensive results and enables calculation of unemployment by different group categories such as race and gender. This method is the most internationally comparable. Official Estimates are determined by a combination of information from one or more of the other three methods. The use of this method has been declining in favor of labour surveys. Social Insurance Statistics, such as unemployment benefits, are computed base on the number of persons insured representing the total labour force and the number of persons who are insured that are collecting benefits. This method has been heavily criticized because if the expiration of benefits before the person finds work. Employment Office Statistics are the least effective since they include only a monthly tally of unemployed persons who enter employment offices. This method also includes those who are not unemployed by the ILO definition.The primary measure of unemployment, U3, allows for comparisons between countries. Unemployment differs from country to country and across different time periods. For example, in the 1990s and 2000s, the United States had lower unemployment levels than many countries in the European Union, which had significant internal variation, with countries like the United Kingdom and Denmark outperforming Italy and France. However, large economic events like the Great Depression can lead to similar unemployment rates across the globe. In 2013, the ILO adopted a resolution to introduce new indicators to measure the unemployment rate. LU1: Unemployment rate: [persons in unemployment / labour force] × 100 LU2: Combined rate of time-related underemployment and unemployment: [(persons in time-related underemployment + persons in unemployment) / labour force]x 100 LU3: Combined rate of unemployment and potential labour force: [(persons in unemployment + potential labour force) / (extended labour force)] × 100 LU4: Composite measure of labour underutilization: [(persons in time-related underemployment + persons in unemployment + potentiallabour force) / (extended labour force)] × 100 European Union (Eurostat) Eurostat, the statistical office of the European Union, defines unemployed as those persons between age 15 and 74 who are not working, have looked for work in the last four weeks, and are ready to start work within two weeks; this definition conforms to ILO standards. Both the actual count and the unemployment rate are reported. Statistical data are available by member state for the European Union as a whole (EU28) as well as for the eurozone (EA19). Eurostat also includes a long-term unemployment rate, which is defined as part of the unemployed who have been unemployed for more than one year.The main source used is the European Union Labour Force Survey (EU-LFS). It collects data on all member states each quarter. For monthly calculations, national surveys or national registers from employment offices are used in conjunction with quarterly EU-LFS data. The exact calculation for individual countries, resulting in harmonized monthly data, depends on the availability of the data. United States Bureau of Labor statistics The Bureau of Labor Statistics measures employment and unemployment (of those over 17 years of age) by using two different labor force surveys conducted by the United States Census Bureau (within the United States Department of Commerce) and/or the Bureau of Labor Statistics (within the United States Department of Labor) that gather employment statistics monthly. The Current Population Survey (CPS), or "Household Survey," conducts a survey based on a sample of 60,000 households. The survey measures the unemployment rate based on the ILO definition.The Current Employment Statistics survey (CES), or "Payroll Survey," conducts a survey based on a sample of 160,000 businesses and government agencies, which represent 400,000 individual employers. Since the survey measures only civilian nonagricultural employment, it does not calculate an unemployment rate, and it differs from the ILO unemployment rate definition. Both sources have different classification criteria and usually produce differing results. Additional data are also available from the government, such as the unemployment insurance weekly claims report available from the Office of Workforce Security, within the U.S. Department of Labors Employment and Training Administration. The Bureau of Labor Statistics provides up-to-date numbers via a PDF linked here. The BLS also provides a readable concise current Employment Situation Summary, updated monthly. The Bureau of Labor Statistics also calculates six alternate measures of unemployment, U1 to U6, which measure different aspects of unemployment: U1: Percentage of labor force unemployed 15 weeks or longer. U2: Percentage of labor force who lost jobs or completed temporary work. U3: Official unemployment rate, per the ILO definition, occurs when people are without jobs and they have actively looked for work within the past four weeks. U4: U3 + "discouraged workers", or those who have stopped looking for work because current economic conditions make them believe that no work is available for them. U5: U4 + other "marginally attached workers," or "loosely attached workers," or those who "would like" and are able to work but have not looked for work recently. U6: U5 + Part-time workers who want to work full-time, but cannot for economic reasons (underemployment).Note: "Marginally attached workers" are added to the total labour force for unemployment rate calculation for U4, U5, and U6. The BLS revised the CPS in 1994 and among the changes the measure representing the official unemployment rate was renamed U3 instead of U5. In 2013, Representative Hunter proposed that the Bureau of Labor Statistics use the U5 rate instead of the current U3 rate.Statistics for the US economy as a whole hide variations among groups. For example, in January 2008, the US unemployment rates were 4.4% for adult men, 4.2% for adult women, 4.4% for Caucasians, 6.3% for Hispanics or Latinos (all races), 9.2% for African Americans, 3.2% for Asian Americans, and 18.0% for teenagers. Also, the US unemployment rate would be at least 2% higher if prisoners and jail inmates were counted.The unemployment rate is included in a number of major economic indices including the US Conference Boards Index of Leading Indicators a macroeconomic measure of the state of the economy. Alternatives Limitations of definition Some critics believe that current methods of measuring unemployment are inaccurate in terms of the impact of unemployment on people as these methods do not take into account the 1.5% of the available working population incarcerated in US prisons (who may or may not be working while they are incarcerated); those who have lost their jobs and have become discouraged over time from actively looking for work; those who are self-employed or wish to become self-employed, such as tradesmen or building contractors or information technology consultants; those who have retired before the official retirement age but would still like to work (involuntary early retirees); those on disability pensions who do not possess full health but still wish to work in occupations that suitable for their medical conditions; or those who work for payment for as little as one hour per week but would like to work full time.The last people are "involuntary part-time" workers, those who are underemployed, such as a computer programmer who is working in a retail store until he can find a permanent job, involuntary stay-at-home mothers who would prefer to work, and graduate and professional school students who are unable to find worthwhile jobs after they graduated with their bachelors degrees. Internationally, some nations unemployment rates are sometimes muted or appear less severe because of the number of self-employed individuals working in agriculture. Small independent farmers are often considered self-employed and so cannot be unemployed. That can impact non-industrialized economies, such as the United States and Europe in the early 19th century, since overall unemployment was approximately 3% because so many individuals were self-employed, independent farmers; however, non-agricultural unemployment was as high as 80%.Many economies industrialize and so experience increasing numbers of non-agricultural workers. For example, the United States non-agricultural labour force increased from 20% in 1800 to 50% in 1850 and 97% in 2000. The shift away from self-employment increases the percentage of the population that is included in unemployment rates. When unemployment rates between countries or time periods are compared, it is best to consider differences in their levels of industrialization and self-employment. Additionally, the measures of employment and unemployment may be "too high." In some countries, the availability of unemployment benefits can inflate statistics by giving an incentive to register as unemployed. People who do not seek work may choose to declare themselves unemployed to get benefits; people with undeclared paid occupations may try to get unemployment benefits in addition to the money that they earn from their work.However, in the United States,

Unemployment

Canada, Mexico, Australia, Japan, and the European Union, unemployment is measured using a sample survey (akin to a Gallup poll). According to the BLS, a number of Eastern European nations have instituted labour force surveys as well. The sample survey has its own problems because the total number of workers in the economy is calculated based on a sample, rather than a census. It is possible to be neither employed nor unemployed by ILO definitions by being outside of the "labour force." Such people have no job and are not looking for one. Many of them go to school or are retired. Family responsibilities keep others out of the labour force. Still others have a physical or mental disability that prevents them from participating in the labour force. Some people simply elect not to work and prefer to be dependent on others for sustenance. Typically, employment and the labour force include only work that is done for monetary gain. Hence, a homemaker is neither part of the labour force nor unemployed. Also, full-time students and prisoners are considered to be neither part of the labour force nor unemployed. The number of prisoners can be important. In 1999, economists Lawrence F. Katz and Alan B. Krueger estimated that increased incarceration lowered measured unemployment in the United States by 0.17% between 1985 and the late 1990s.In particular, as of 2005, roughly 0.7% of the US population is incarcerated (1.5% of the available working population). Additionally, children, the elderly, and some individuals with disabilities are typically not counted as part of the labour force and so are not included in the unemployment statistics. However, some elderly and many disabled individuals are active in the labour market. In the early stages of an economic boom, unemployment often rises. That is because people join the labour market (give up studying, start a job hunt, etc.) as a result of the improving job market, but until they have actually found a position, they are counted as unemployed. Similarly, during a recession, the increase in the unemployment rate is moderated by people leaving the labour force or being otherwise discounted from the labour force, such as with the self-employed. For the fourth quarter of 2004, according to OECD (Employment Outlook 2005 ISBN 92-64-01045-9), normalized unemployment for men aged 25 to 54 was 4.6% in the US and 7.4% in France. At the same time and for the same population, the employment rate (number of workers divided by population) was 86.3% in the US and 86.7% in France. That example shows that the unemployment rate was 60% higher in France than in the US, but more people in that demographic were working in France than in the US, which is counterintuitive if it is expected that the unemployment rate reflects the health of the labour market.Those deficiencies make many labour market economists prefer to look at a range of economic statistics such as labour market participation rate, the percentage of people between 15 and 64 who are currently employed or searching for employment, the total number of full-time jobs in an economy, the number of people seeking work as a raw number and not a percentage, and the total number of person-hours worked in a month compared to the total number of person-hours people would like to work. In particular, the National Bureau of Economic Research does not use the unemployment rate but prefers various employment rates to date recessions. Labor force participation rate The labor force participation rate is the ratio between the labor force and the overall size of their cohort (national population of the same age range). In the West, during the later half of the 20th century, the labor force participation rate increased significantly because of an increase in the number of women entering the workplace. In the United States, there have been four significant stages of womens participation in the labour force: increases in the 20th century and decreases in the 21st century. Male labor force participation decreased from 1953 to 2013. Since October 2013, men have been increasingly joining the labour force. From the late 19th century to the 1920s, very few women worked outside the home. They were young single women who typically withdrew from the labor force at marriage unless family needed two incomes. Such women worked primarily in the textile manufacturing industry or as domestic workers. That profession empowered women and allowed them to earn a living wage. At times, they were a financial help to their families. Between 1930 and 1950, female labor force participation increased primarily because of the increased demand for office workers, womens participation in the high school movement, and electrification, which reduced the time that was spent on household chores. From the 1950s to the early 1970s, most women were secondary earners working mainly as secretaries, teachers, nurses, and librarians (pink-collar jobs). From the mid-1970s to the late 1990s, there was a period of revolution of women in the labor force brought on by various factors, many of which arose from the second-wave feminism movement. Women more accurately planned for their future in the work force by investing in more applicable majors in college that prepared them to enter and compete in the labor market. In the United States, the female labor force participation rate rose from approximately 33% in 1948 to a peak of 60.3% in 2000. As of April 2015, the female labor force participation is at 56.6%, the male labor force participation rate is at 69.4%, and the total is 62.8%.A common theory in modern economics claims that the rise of women participating in the US labor force in the 1950s to the 1990s was caused by the introduction of a new contraceptive technology, birth control pills, as well as the adjustment of age of majority laws. The use of birth control gave women the flexibility of opting to invest and to advance their career while they maintained a relationship. By having control over the timing of their fertility, they were not running a risk of thwarting their career choices. However, only 40% of the population actually used the birth control pill. That implies that other factors may have contributed to women choosing to invest in advancing their careers. One factor may be that an increasing number of men delayed the age of marriage, which allowed women to marry later in life without them worrying about the quality of older men. Other factors include the changing nature of work, with machines replacing physical labor, thus eliminating many traditional male occupations, and the rise of the service sector in which many jobs are gender neutral. Another factor that may have contributed to the trend was the Equal Pay Act of 1963, which aimed at abolishing wage disparity based on sex. Such legislation diminished sexual discrimination and encouraged more women to enter the labor market by receiving fair remuneration to help raising families and children. At the turn of the 21st century, the labor force participation began to reverse its long period of increase. Reasons for the change include a rising share of older workers, an increase in school enrollment rates among young workers, and a decrease in female labor force participation.The labor force participation rate can decrease when the rate of growth of the population outweighs that of the employed and the unemployed together. The labor force participation rate is a key component in long-term economic growth, almost as important as productivity. A historic shift began around the end of the Great Recession as women began leaving the labor force in the United States and other developed countries. The female labor force participation rate in the United States has steadily decreased since 2009, and as of April 2015, the female labor force participation rate has gone back down to 1988 levels of 56.6%.Participation rates are defined as follows: The labor force participation rate explains how an increase in the unemployment rate can occur simultaneously with an increase in employment. If a large number of new workers enter the labor force but only a small fraction become employed, then the increase in the number of unemployed workers can outpace the growth in employment. Unemployment-to-population ratio The unemployment-to-population ratio calculates the share of unemployed for the whole population. This is in contrast to the unemployment rate, which calculates the percentage of unemployed persons in relation to the active population. Particularly, many young people between 15 and 24 are studying full-time and so are neither working nor looking for a job. That means that they are not part of the labor force, which is used as the denominator when the unemployment rate is calculated.The youth unemployment ratios in the European Union range from 5.2 (Austria) to 20.6 percent (Spain). They are considerably lower than the standard youth unemployment rates, ranging from 7.9 (Germany) to 57.9 percent (Greece). Effects High and the persistent unemployment, in which economic inequality increases, has a negative effect on subsequent long-run economic growth. Unemployment can harm growth because it is a waste of resources; generates redistributive pressures and subsequent distortions; drives people to poverty; constrains liquidity limiting labor mobility; and erodes self-esteem promoting social dislocation, unrest, and conflict. The 2013 winner of the Nobel Prize in Economics, Robert J. Shiller, said that rising inequality in the United States and elsewhere is the most important problem. Costs Individual Unemployed individuals are unable to earn money to meet financial obligations. Failure to pay mortgage payments or to pay rent may lead to homelessness through foreclosure or eviction. Across the United States the growing ranks of people made homeless in the foreclosure crisis are generating tent cities.Unemployment increases susceptibility to cardiovascular disease, somatization, anxiety disorders, depression, and suicide. In addition, unemployed people have higher rates of medication use, poor diet, physician visits, tobacco smoking, alcoholic beverage consumption, drug use, and lower rates of exercise. According to a study published in Social Indicator Research, even those who tend to be optimistic find it difficult to look on the bright side of things when unemployed. Using interviews and data from German participants aged 16 to 94, including individuals coping with the stresses of real life and not just a volunteering student population, the researchers determined that even optimists struggled with being unemployed.In 1979, M. Harvey Brenner found that for every 10% increase in the number of unemployed, there is an increase of 1.2% in total mortality, a 1.7% increase in cardiovascular disease, 1.3% more cirrhosis cases, 1.7% more suicides, 4.0% more arrests, and 0.8% more assaults reported to the police.A study by Christopher Ruhm in 2000 on the effect of recessions on health found that several measures of health actually improve during recessions. As for the impact of an economic downturn on crime, during the Great Depression, the crime rate did not decrease. The unemployed in the US often use welfare programs such as food stamps or accumulating debt because unemployment insurance in the US generally does not replace most of the income that was received on the job, and one cannot receive such aid indefinitely. Not everyone suffers equally from unemployment. In a prospective study of 9,570 individuals over four years, highly-conscientious people suffered more than twice as much if they became unemployed. The authors suggested that may because of conscientious people making different attributions about why they became unemployed or through experiencing stronger reactions following failure. There is also the possibility of reverse causality from poor health to unemployment.Some researchers hold that many of the low-income jobs are not really a better option than unemployment with a welfare state, with its unemployment insurance benefits. However, since it is difficult or impossible to get unemployment insurance benefits without having worked in the past, those jobs and unemployment are more complementary than they are substitutes. (They are often held short-term, either by students or by those trying to gain experience; turnover in most low-paying jobs is high.) Another cost for the unemployed is that the combination of unemployment, lack of financial resources, and social responsibilities may push unemployed workers to take jobs that do not fit their skills or allow them to use their talents. Unemployment can cause underemployment, and fear of job loss can spur psychological anxiety. As well as anxiety, it can cause depression, lack of confidence, and huge amounts of stress, which is increased when the unemployed are faced with health issues, poverty, and lack of relational support.Another personal cost of unemployment is its impact on relationships. A 2008 study from Covizzi, which examined the relationship between unemployment and divorce, found that the rate of divorce is greater for couples when one partner is unemployed. However, a more recent study has found that some couples often stick together in "unhappy" or "unhealthy" marriages when they are unemployed to buffer financial costs. A 2014 study by Van der Meer found that the stigma that comes from being unemployed affects personal well-being, especially for men, who often feel as though their masculine identities are threatened by unemployment.Unemployment can also bring personal costs in relation to gender. One study found that women are more likely to experience unemployment than men and that they are less likely to move from temporary positions to permanent positions. Another study on gender and unemployment found that men, however, are more likely to experience greater stress, depression, and adverse effects from unemployment, largely stemming from the perceived threat to their role as breadwinner. The study found that men expect themselves to be viewed as "less manly" after a job loss than they actually are and so they engage in compensating behaviors, such as financial risk-taking and increased assertiveness. Unemployment has been linked to extremely adverse effects on mens mental health. Professor Ian Hickie of the University of Sydney said that evidence showed that men have more restricted social networks than women and that men have are heavily work-based. Therefore, the loss of a job for men means the loss of a whole set of social connections as well. That loss can then lead to men becoming socially isolated very quickly. An Australian study on the mental health impacts of graduating during an economic downturn found that the negative mental health outcomes are greater and more scarring for men than women. The effect was particularly pronounced for those with vocational or secondary education.Costs of unemployment also vary depending on age. The young and the old are the two largest age groups currently experiencing unemployment. A 2007 study from Jacob and Kleinert found that young people (ages 18 to 24) who have fewer resources and limited work experiences are more likely to be unemployed. Other researchers have found that todays high school seniors place a lower value on work than those in the past, which is likely because they recognize the limited availability of jobs. At the other end of the age spectrum, studies have found that older individuals have more barriers than younger workers to employment, require stronger social networks to acquire work, and are also less likely to move from temporary to permanent positions. Additionally, some older people see age discrimination as the reason for them not getting hired. Social An economy with high unemployment is not using all of the resources, specifically labour, available to it. Since it is operating below its production possibility frontier, it could have higher output if all of the workforce were usefully employed. However, there is a tradeoff between economic efficiency and unemployment: if all frictionally unemployed accepted the first job that they were offered, they would be likely to be operating at below their skill level, reducing the economys efficiency.During a long period of unemployment, workers can lose their skills, causing a loss of human capital. Being unemployed can also reduce the life expectancy of workers by about seven years.High unemployment can encourage xenophobia and protectionism since workers fear that foreigners are stealing their jobs. Efforts to preserve existing jobs of domestic and native workers include legal barriers against "outsiders" who want jobs, obstacles to immigration, and/or tariffs and similar trade barriers against foreign competitors. High unemployment can also cause social problems such as crime. If people have less disposable income than before, it is very likely that crime levels within the economy will increase. A 2015 study published in The Lancet, estimates that unemployment causes 45,000 suicides a year globally. Sociopolitical High levels of unemployment can be causes of civil unrest, in some cases leading to revolution, particularly totalitarianism. The fall of the Weimar Republic in 1933 and Adolf Hitlers rise to power, which culminated in World War II and the deaths of tens of millions and the destruction of much of the physical capital of Europe, is attributed to the poor economic conditions in Germany at the time, notably a high unemployment rate of above 20%; see Great Depression in Central Europe for details. However the hyperinflation in the Weimar Republic is not directly blamed for the Nazi rise. Hyperinflation occurred primarily in 1921 to 1923, the year of Hitlers Beer Hall Putsch. Although hyperinflation has been blamed for damaging the credibility of democratic institutions, the Nazis did not assume government until 1933, ten years after the hyperinflation but in the midst of high unemployment. Rising unemployment has traditionally been regarded by the public and the media in any country as a key guarantor of electoral defeat for any government that oversees it. That was very much the consensus in the United Kingdom until 1983, when Thatchers Conservative government won a landslide in the general election, despite overseeing a rise in unemployment from 1.5 million to 3.2 million since the 1979 election. Benefits The primary benefit of unemployment is that people are available for hire, without being headhunted away from their existing employers. That permits both new and old businesses to take on staff. Unemployment is argued to be "beneficial" to the people who are not unemployed in the sense that it averts inflation, which itself has damaging effects, by providing (in Marxian terms) a reserve army of labour, which keeps wages in check. However, the direct connection between full local employment and local inflation has been disputed by some because of the recent increase in international trade that supplies low-priced goods even while local employment rates rise to full employment. Full employment cannot be achieved because workers would shirk if they were not threatened with the possibility of unemployment. The curve for the no-shirking condition (labelled NSC) thus goes to infinity at full employment. The inflation-fighting benefits to the entire economy arising from a presumed optimum level of unemployment have been studied extensively. The Shapiro–Stiglitz model suggests that wages never bid down sufficiently to reach 0% unemployment. That occurs because employers know that when wages decrease, workers will shirk and expend less effort. Employers avoid shirking by preventing wages from decreasing so low that workers give up and become unproductive. The higher wages perpetuate unemployment, but the threat of unemployment reduces shirking. Before current levels of world trade were developed, unemployment was shown to reduce inflation, following the Phillips curve, or to decelerate inflation, following the NAIRU/natural rate of unemployment theory since it is relatively easy to seek a new job without losing a current job. When more jobs are available for fewer workers (lower unemployment), that may allow workers to find the jobs that better fit their tastes, talents and needs. As in the Marxian theory of unemployment, special interests may also benefit. Some employers may expect that employees with no fear of losing their jobs will not work as hard or will demand increased wages and benefit. According to that theory, unemployment may promote general labour productivity and profitability by increasing employers rationale for their monopsony-like power (and profits).Optimal unemployment has also been defended as an environmental tool to brake the constantly-accelerated growth of the GDP to maintain levels that are sustainable in the context of resource constraints and environmental impacts. However, the tool of denying jobs to willing workers seems a blunt instrument for conserving resources and the environment. It reduces the consumption of the unemployed across the board and only in the short term. Full employment of the unemployed workforce, all focused toward the goal of developing more environmentally-efficient methods for production and consumption, might provide a more significant and lasting cumulative environmental benefit and reduced resource consumption.Some critics of the "culture of work" such as the anarchist Bob Black see employment as culturally overemphasized in modern countries. Such critics often propose quitting jobs when possible, working less, reassessing the cost of living to that end, creation of jobs that are "fun" as opposed to "work," and creating cultural norms in which work is seen as unhealthy. These people advocate an "anti-work" ethic for life. Decline in work hours As a result of productivity, the work week declined considerably during the 19th century. By the 1920s, the average workweek in the US was 49 hours, but it was reduced to 40 hours (after which overtime premium was applied) as part of the 1933 National Industrial Recovery Act. During the Great Depression, the enormous productivity gains caused by electrification, mass production, and agricultural mechanization were believed to have ended the need for a large number of previously-employed workers. Remedies Societies try a number of different measures to get as many people as possible into work, and various societies have experienced close to full employment for extended periods, particularly during the post-World War II economic expansion. The United Kingdom in the 1950s and 1960s averaged 1.6% unemployment, and in Australia, the 1945 White Paper on Full Employment in Australia established a government policy of full employment, which lasted until the 1970s.However, mainstream economic discussions of full employment since the 1970s suggest that attempts to reduce the level of unemployment below the natural rate of unemployment will fail but result only in less output and more inflation. Demand-side solutions Increases in the demand for labour move the economy along the demand curve, increasing wages and employment. The demand for labour in an economy is derived from the demand for goods and services. As such, if the demand for goods and services in the economy increases, the demand for labour will increase, increasing employment and wages. There are many ways to stimulate demand for goods and services. Increasing wages to the working class (those more likely to spend the increased funds on goods and services, rather than various types of savings or commodity purchases) is one theory that is proposed. Increased wages are believed to be more effective in boosting demand for goods and services than central banking strategies, which put the increased money supply mostly into the hands of wealthy persons and institutions. Monetarists suggest that increasing money supply in general increases short-term demand. As for the long-term demand, the increased demand is negated by inflation. A rise in fiscal expenditures is another strategy for boosting aggregate demand. Providing aid to the unemployed is a strategy that is used to prevent cutbacks in consumption of goods and services, which can lead to a vicious cycle of further job losses and further decreases in consumption and demand. Many countries aid the unemployed through social welfare programs. Such unemployment benefits include unemployment insurance, unemployment compensation, welfare, and subsidies to aid in retraining. The main goal of such programs is to alleviate short-term hardships and, more importantly, to allow workers more time to search for a job. A direct demand-side solution to unemployment is government-funded employment of the able-bodied poor. This was notably implemented in Britain from the 17th century until 1948 in the institution of the workhouse, which provided jobs for the unemployed with harsh conditions and poor wages to dissuade their use. A modern alternative is a job guarantee in which the government guarantees work at a living wage. Temporary measures can include public works programs such as the Works Progress Administration. Government-funded employment is not widely advocated as a solution to unemployment except in times of crisis. That is attributed to the public sector jobs existence depending directly on the tax receipts from private sector employment. In the US, the unemployment insurance allowance is based solely on previous income (not time worked, family size, etc.) and usually compensates for one third of previous income. To qualify, people must reside in their respective state for at least a year and work. The system was established by the Social Security Act of 1935. Although 90% of citizens are covered by unemployment insurance, less than 40% apply for and receive benefits. However, the number applying for and receiving benefits increases during recessions. For highly-seasonal industries, the system provides income to workers during the off-season, thus encouraging them to stay attached to the industry. According to classical economic theory, markets reach equilibrium where supply equals demand; everyone who wants to sell at the market price can do so. Those who do not want to sell at that price do not; in the labour market, this is classical unemployment. Monetary policy and fiscal policy can both be used to increase short-term growth in the economy, increasing the demand for labour and decreasing unemployment. Supply-side solutions However, the labor market is not 100% efficient although it may be more efficient than the bureaucracy. Some argue that minimum wages and union activity keep wages from falling, which means that too many people want to sell their labour at the going price but cannot. That assumes perfect competition exists in the labour market, specifically that no single entity is large enough to affect wage levels and that employees are similar in ability. Advocates of supply-side policies believe those policies can solve the problem by making the labour market more flexible. These include removing the minimum wage and reducing the power of unions. Supply-siders argue that their reforms increase long-term growth by reducing labour costs. The increased supply of goods and services requires more workers, increasing employment. It is argued that supply-side policies, which include cutting taxes on businesses and reducing regulation, create jobs, reduce unemployment, and decrease labors share of national income. Other supply-side policies include education to make workers more attractive to employers. History There are relatively limited historical records on unemployment because it has not always been acknowledged or measured systematically. Industrialization involves economies of scale, which often prevent individuals from having the capital to create their own jobs to be self-employed. An individual who cannot join an enterprise or create a job is unemployed. As individual farmers, ranchers, spinners, doctors and merchants are organized into large enterprises, those who cannot join or compete become unemployed. Recognition of unemployment occurred slowly as economies across the world industrialized and bureaucratized. Before that, traditional self-sufficient native societies had no concept of unemployment. The recognition of the concept of "unemployment" is best exemplified through the well documented historical records in England. For example, in 16th-century, England no distinction was made between vagrants and the jobless; both were simply categorized as "sturdy beggars", who were to be punished and moved on. 16th century The closing of the monasteries in the 1530s increased poverty, as the Roman Catholic Church had helped the poor. In addition, there was a significant rise in enclosures during the Tudor period. Also, the population was rising. Those unable to find work had a stark choice: starve or break the law. In 1535, a bill was drawn up calling for the creation of a system of public works to deal with the problem of unemployment, which were to be funded by a tax on income and capital. A law that was passed a year later allowed vagabonds to be whipped and hanged.In 1547, a bill was passed that subjected vagrants to some of the more extreme provisions of the criminal law: two years servitude and branding with a "V" as the penalty for the first offense and death for the second. During the reign of Henry VIII, as many as 72,000 people are estimated to have been executed. In the 1576 Act, each town was required to provide work for the unemployed.The Elizabethan Poor Law of 1601, one of the worlds first government-sponsored welfare programs, made a clear distinction between those who were unable to work and those able-bodied people who refused employment. Under the Poor Law systems of England and Wales, Scotland and Ireland, a workhouse was a place people unable to support themselves could go to live and work. Industrial Revolution to late 19th century Poverty was a highly visible problem in the eighteenth century, both in cities and in the countryside. In France and Britain by the end of the century, an estimated 10 percent of the people depended on charity or begging for their food. By 1776, some 1,912 parish and corporation workhouses had been established in England and Wales and housed almost 100,000 paupers. A description of the miserable living standards of the mill workers in England in 1844 was given by Fredrick Engels in The Condition of the Working Class in England in 1844. In the preface to the 1892 edition, Engels noted that the extreme poverty he had written about in 1844 had largely disappeared. David Ames Wells also noted that living conditions in England had improved near the end of the 19th century and that unemployment was low. The scarcity and the high price of labor in the US in the 19th century

Unemployment

was well documented by contemporary accounts, as in the following: "The laboring classes are comparatively few in number, but this is counterbalanced by, and indeed, may be one of the causes of the eagerness by which they call in the use of machinery in almost every department of industry. Wherever it can be applied as a substitute for manual labor, it is universally and willingly resorted to.... It is this condition of the labor market, and this eager resort to machinery wherever it can be applied, to which, under the guidance of superior education and intelligence, the remarkable prosperity of the United States is due." Scarcity of labor was a factor in the economics of slavery in the United States. As new territories were opened and federal land sales were conducted, land had to be cleared and new homesteads established. Hundreds of thousands of immigrants annually came to the US and found jobs digging canals and building railroads. Almost all work during most of the 19th century was done by hand or with horses, mules, or oxen since there was very little mechanization. The workweek during most of the 19th century was 60 hours. Unemployment at times was between one and two percent. The tight labor market was a factor in productivity gains by allowing workers to maintain or to increase their nominal wages during the secular deflation that caused real wages to rise at various times in the 19th century, especially in its final decades. 20th century There were labor shortages during World War I. Ford Motor Co. doubled wages to reduce turnover. After 1925, unemployment gradually began to rise.The 1930s saw the Great Depression impact unemployment across the globe. In Germany and the United States, the unemployment rate reached about 25% in 1932.In some towns and cities in the northeast of England, unemployment reached as high as 70%; the national unemployment level peaked at more than 22% in 1932. Unemployment in Canada reached 27% at the depth of the Depression in 1933. In 1929, the U.S. unemployment rate averaged 3%. In the US, the Works Progress Administration (1935–43) was the largest make-work program. It hired men (and some women) off the relief roles ("dole") typically for unskilled labor. During the New Deal, over three million unemployed young men were taken out of their homes and placed for six months into more than 2600 work camps managed by the Civilian Conservation Corps.Unemployment in the United Kingdom fell later in the 1930s as the Depression eased, and it remained low (in single figures) after World War II. Fredrick Mills found that in the US, 51% of the decline in work hours was due to the fall in production and 49% was from increased productivity.By 1972, unemployment in the United Kingdom had crept back up above 1,000,000, and it was even higher by the end of the decade, with inflation also being high. Although the monetarist economic policies of Margaret Thatchers Conservative government saw inflation reduced after 1979, unemployment soared in the early 1980s and in 1982, it exceeded 3,000,000, a level that had not been seen for some 50 years. That represented one in eight of the workforce, with unemployment exceeding 20% in some places that had relied on declining industries such as coal mining.However, it was a time of high unemployment in all other major industrialised nations as well. By the spring of 1983, unemployment had risen by 6% in the previous 12 months, compared to 10% in Japan, 23% in the US, and 34% in West Germany (seven years before Reunification).Unemployment in the United Kingdom remained above 3,000,000 until the spring of 1987, when the economy enjoyed a boom. By the end of 1989, unemployment had fallen to 1,600,000. However, inflation had reached 7.8%, and the following year, it reached a nine-year high of 9.5%; leading to increased interest rates.Another recession occurred from 1990 to 1992. Unemployment began to increase, and by the end of 1992, nearly 3,000,000 in the United Kingdom were unemployed, a number that was soon lowered by a strong economic recovery. With inflation down to 1.6% by 1993, unemployment then began to fall rapidly and stood at 1,800,000 by early 1997. 21st century The official unemployment rate in the 16 European Union (EU) countries that use the euro rose to 10% in December 2009 as a result of another recession. Latvia had the highest unemployment rate in the EU, at 22.3% for November 2009. Europes young workers have been especially hard hit. In November 2009, the unemployment rate in the EU27 for those aged 15–24 was 18.3%. For those under 25, the unemployment rate in Spain was 43.8%. Unemployment has risen in two thirds of European countries since 2010.Into the 21st century, unemployment in the United Kingdom remained low and the economy remaining strong, and several other European economies, such as France and Germany, experienced a minor recession and a substantial rise in unemployment.In 2008, when the recession brought on another increase in the United Kingdom, after 15 years of economic growth and no major rises in unemployment. In early 2009, unemployment passed the 2 million mark, and economists were predicting it would soon reach 3 million. However, the end of the recession was declared in January 2010 and unemployment peaked at nearly 2.7 million in 2011, appearing to ease fears of unemployment reaching 3 million. The unemployment rate of Britains young black people was 47.4% in 2011. 2013/2014 has seen the employment rate increase from 1,935,836 to 2,173,012 as supported by showing the UK is creating more job opportunities and forecasts the rate of increase in 2014/2015 will be another 7.2%.The 2008–2012 global recession has been called a "mancession" because of the disproportionate number of men who lost their jobs as compared to women. The gender gap became wide in the United States in 2009, when 10.5% of men in the labor force were unemployed, compared with 8% of women. Three quarters of the jobs that were lost in the recession in the US were held by men.A 26 April 2005 Asia Times article noted, "In regional giant South Africa, some 300,000 textile workers have lost their jobs in the past two years due to the influx of Chinese goods". The increasing US trade deficit with China cost 2.4 million American jobs between 2001–2008, according to a study by the Economic Policy Institute (EPI). From 2000–2007, the United States lost a total of 3.2 million manufacturing jobs. 12.1% of US military veterans who had served after the September 11 attacks in 2001 were unemployed as of 2011; 29.1% of male veterans aged 18–24 were unemployed. As of September 2016, the total veteran unemployment rate was 4.3 percent. By September 2017, that figure had dropped to 3 percent.About 25,000,000 people in the worlds 30 richest countries lost their jobs between the end of 2007 and the end of 2010, as the economic downturn pushed most countries into recession. In April 2010, the US unemployment rate was 9.9%, but the governments broader U-6 unemployment rate was 17.1%. In April 2012, the unemployment rate was 4.6% in Japan. In a 2012 story, the Financial Post reported, "Nearly 75 million youth are unemployed around the world, an increase of more than 4 million since 2007. In the European Union, where a debt crisis followed the financial crisis, the youth unemployment rate rose to 18% last year from 12.5% in 2007, the ILO report shows." In March 2018, according to US Unemployment Rate Statistics, the unemployment rate was 4.1%, below the 4.5–5.0% norm. See also Notes References Farmer, Roger E. A. (2001). "Unemployment". Macroeconomics (Second ed.). Cincinnati: South-Western Publishing. pp. 173–192. ISBN 978-0-324-14964-7. Kalecki, Michał (1943). "Political aspects of full employment" (PDF). The Political Quarterly. 14 (4): 322–331. doi:10.1111/j.1467-923X.1943.tb01016.x. McGaughey, Ewan (10 January 2018). "Will Robots Automate Your Job Away? Full Employment, Basic Income, and Economic Democracy". Centre for Business Research, University of Cambridge, Working Paper No. 496. doi:10.2139/ssrn.3044448. S2CID 219336439. SSRN 3044448. Reich, Robert B. (2010). Aftershock: The Next Economy and Americas Future (1st ed.). Alfred A. Knopf. ISBN 978-0-307-59281-1. Romer, David (2011). "Unemployment". Advanced Macroeconomics (Fourth ed.). New York: McGraw-Hill Education. pp. 456–512. ISBN 978-0-07-351137-5. Simonazzi, Annamaria; Vianello, Fernando (2001). "Financial Liberalization, the European Single Currency and the Problem of Unemployment". In Franzini, M.; Pizzuti, F. R. (eds.). Globalization, Institutions and Social Cohesion. Heidelberg: Springer. ISBN 978-3-540-67741-3. Historical: Europe and Japan Beveridge, William H. (1944). Full Employment in a Free Society (1st ed.). Allen & Unwin., in Great Britain. Broadberry, Stephen N., and Albrecht Ritschl. "Real Wages, Productivity, and Unemployment in Britain and Germany during the 1920s." Explorations in Economic History 32.3 (1995): 327-349. Dimsdale, Nicholas H., Nicholas Horsewood, and Arthur Van Riel. "Unemployment in interwar Germany: an analysis of the labor market, 1927-1936." Journal of Economic History (2006): 778-808. online Heimberger, Philipp, Jakob Kapeller, and Bernhard Schütz. "The NAIRU determinants: What’s structural about unemployment in Europe?." Journal of Policy Modeling 39.5 (2017): 883-908. online Kato, Michiya. "Unemployment and Public Works Policy in Interwar Britain and Japan: An International Comparison." (2010): 69-101. online Kaufman, Roger T. "Patterns of Unemployment in North America, Western Europe and Japan." Unemployment in Western countries (Palgrave Macmillan, 1980). 3-35. Nickell, Stephen, Luca Nunziata, and Wolfgang Ochel. "Unemployment in the OECD since the 1960s. What do we know?." Economic Journal 115.500 (2005): 1-27 online. Stachura, Peter D., ed. Unemployment and the great depression in Weimar Germany (Springer, 1986). Topp, Niels-Henrik. "Unemployment and Economic Policy in Denmark in the 1930s." Scandinavian Economic History Review 56.1 (2008): 71-90. Webb, Sidney (1912). How the Government Can Prevent Unemployment. The National Committee for the Prevention of Destitution. (First ed.). Letchworth, Herts.: Garden City Press Ltd., in Great Britain Historical: United States Jensen, Richard J. "The causes and cures of unemployment in the Great Depression." Journal of Interdisciplinary History 19.4 (1989): 553-583 online. Keyssar, Alexander (1986). Out of Work: The First Century of Unemployment in Massachusetts. Cambridge University Press. ISBN 978-0-521-23016-2. Margo, Robert A. "Employment and Unemployment in the 1930s." Journal of Economic Perspectives 7.2 (1993): 41-59. online Stricker, Frank. American Unemployment: Past, Present, and Future (University of Illinois Press, 2020) online review Sundstrom, William A. "Last hired, first fired? Unemployment and urban black workers during the Great Depression." Journal of Economic History (1992): 415-429. online Temin, Peter. "Socialism and Wages in the Recovery from the Great Depression in the United States and Germany." Journal of Economic History (1990): 297-307 online. External links Quotations related to unemployment at Wikiquote The dictionary definition of unemployment at Wiktionary Media related to Unemployment at Wikimedia Commons Economic Policy Institute Current unemployment figures, CEIC Data Current unemployment rates by country OECD Unemployment statistics Unemployment statistics by Lebanese-economy-forum, World Bank data JobCity is Right Platform for Govt Jobs Thermal maps of the worlds unemployment percentage rates – by country, 2007–2010

Surgical instrument

A surgical instrument is a tool or device for performing specific actions or carrying out desired effects during a surgery or operation, such as modifying biological tissue, or to provide access for viewing it. Over time, many different kinds of surgical instruments and tools have been invented. Some surgical instruments are designed for general use in all sorts of surgeries, while others are designed for only certain specialties or specific procedures. Classification of surgical instruments helps surgeons to understand the functions and purposes of the instruments. With the goal of optimizing surgical results and performing more difficult operations, more instruments continue to be invented in the modern era. History Many different kinds of surgical instruments and tools have been invented and some have been repurposed as medical knowledge and surgical practices have developed. As surgery practice diversified, some tools are advanced for higher accuracy and stability while some are invented with the completion of medical and scientific knowledge. Two waves in history contributed significantly to the development of surgical tools. In the 1900s, inventions of aseptic surgeries (maintenance of sterile conditions through good hygiene procedures) on the basis of existing antiseptic surgeries (sterilization of tools before, during, and after surgery) led to the manifestations of sale and use of instrument sterilizers, sterile gauze, and cotton. Most importantly, instruments were advanced to be readily and effectively sterilized by replacing wooden and ivory handles with metals. For safety and comfort concerns, the tools are made with as few pieces as possible.Hand surgery emerged as a specialty during World War II, and the tools used by early hand surgeons remain in common use today, and many are identified by the names of those who created them.Individual tools have diverse history development. Below is a brief history of the inventors and tools created for five commonly used surgical tools. Scissors Mayo scissors, created by one of the mayo brothers, was one of the inventions of the Mayo clinic (established by Dr.William Worrall Mayo and his two sons, Dr. William James Mayo and Dr. Charles Horace Mayo in the 1880s). Mayo scissors have semi-blunt ends and they are either straight or curve-bladed. The straight blades are used for cutting tissue near wounds, and curves are used for cutting thick tissue. Metzenbaum scissors were invented by Myron Metzenbaum (1876-1944). This tool was widely used for tonsillectomy (the surgical removal of the tonsils). The lighter and longer handle allows it to be used in tighter operating fields. Knife to Scalpel to Electrocautery Primitive knives were made of perishable materials such as sharp leaf margins or bamboo. After the Dark Ages, Muslims, and later European countries started to develop surgical instruments, scalpels, for cutting. In 1904, King Gillette developed a double-edged safety razor blade with a disposable blade. After 10 years, Morgan Parker, an engineer, developed and patented another type of disposable scalpel, consisting of an overlapping blade locked into a metal handle that allows for easily replacing dull and used blades with fresh sterile blades. Compared to the Gillette ones, this new blade provides stability whilst still being able to exchange blades between uses. Despite the knowledge that heat can control bleeding since the sixth-century BC, it was not until the 18th-century that people started to use electricity to generate heat for cautery. William Stewart Halsted was the pioneer of the technique, which later was called Diathermy. In 1900, physician Joseph Rivière used electrical current to treat a benign carcinomatous ulcer on the dorsum of his patients hand. Then in 1907, Physician Karl Franz Nagelschmidt used diathermy to treat lesions as well as the coagulation of vascular tumors and hemorrhoids. In the early 1900s, William T. Bovie proposed the use of different current (flow of electrical charge of the carrier) for cutting and coagulation. Bovie collaborated with Dr. Harvey Cushing, which led to the birth of “Bovie”, a diathermy apparatus. It allows for careful dissection of tissue while maintaining hemostasis. Retractors During the Renaissance, retractors were lacking so the surgeons uses their fingers to supply the necessary retraction of tissue exploration. Albucasis, a pioneer of modern medicine, devised numerous hooks for surgical retraction including circumcisions, tracheostomies, hemorrhoidectomies, and central extractions in his famous book Al Tasreef Liman ‘Ajaz ‘Aan Al-Taleef around 1000 AD. In the 19th century, Doyen abdominal retractors were invented by French surgeon Eugène-Louis Doyen. The doyen retractors are auto-static, self-retaining retractors that are used primarily in abdominal OB/GYN procedures. It facilitates the completion of difficult surgeries by providing improved exposure. In the late 19th century, Nicholas Senn, an early adopter of Listerism, felt that having a smooth surface on a surgical instrument was important to help to prevent infection. Thus, he developed what is now called the Senn retractor, a double-ended retractor with an end of three bent prongs that may be dull or sharp, and it was often used in plastic or vascular surgery procedures. The Weitlaner retractor, invented by Franz Weitlaner in 1905, is a self-retaining, finger ring retractor with a cam ratchet lock used for holding back tissue and exposing a surgical site that allows the surgeon to activate using a single hand. His invention inspired the invention of more retractors, such as Adson-Beckman retractors for general surgery and Chung retractors for orthopedic surgery. Forceps Back in the 6th century BC, laboring caused a high mortality rate for both mothers and newborns due to the hours or days of the lasting delivery process. This problem led to the establishment of forceps-assisted delivery in the 16th century by the Chamberlen family. Forceps were later developed over several centuries by leading obstetricians of the time including James Simpson, Neville Barnes, and Christian Kielland. Michael Ellis DeBakey invented one of the most common and well-known DeBkey biceps. The vascular atraumatic forceps (DeBakey)were widely used for grasping vascular tissue and causing minimal damage to the vessels. This invention led to the development of the Dacron aortic graft for the repair of aortic aneurysms. Around the mid 1900s, Alfred Washington Adson, a pioneer in neuroscience at Mayo Clinic, invented Adson forceps that allows the lifting and removal of neural tissue. Hemostat/clamp Hemostats are forceps that aim to obliterate the lumen of vessels and to obtain adherence to the crushed surfaces and vascular hemostasis. Originally, this notion of crushing did not exist and arterial catch forceps simply clamped vessels temporarily prior to ligature or cautery. In 1867, Eugene Koeberle, who accidentally found arterial forceps with a catch closure came away spontaneously without the need for ligature, and invented “pince hémostatique,” which have pin and hole catches. In 1882, the Kocher clamp was created by Emil Theodor Kocher, who significantly contributed to thyroidectomies (removal of all or a part of the thyroid gland) and decompressive craniotomy. This invention decreases the risk of contamination while cutting dense tissue. Later, Dr. William Henry Welch and William Stewart Halsted contributed to the invention of clamps and Halsted-Mosquito Hemostats, which were used to clamp small blood vessels. Kelly clamp, invented by Howard Kelly, has similar functions but it can clamp larger vessels due to the slightly larger jaw.Accordingly, the nomenclature of surgical instruments follows certain patterns, such as a description of the action it performs (for example, scalpel, hemostat), the name of its inventor(s) (for example, the Kocher forceps), or a compound scientific name related to the kind of surgery (for example, a tracheotomy is a tool used to perform a tracheotomy). Classification There are several classes of surgical instruments: Graspers, such as forceps (non-locking forceps/ grasping forceps, thumb forceps, pick-ups) Used for tissue or object grasping. Forceps are categorized into toothed or non-toothed at the tip. (e.g.,Tissue forceps, Adson forceps, Bonney forceps, DeBakey forceps, Russian forceps) Clamps (locking forceps) Clamps stabilize or hold tissue and objects in place. They can be used for traumatic or atraumatic purposes. (e.g., Crile hemostat, Kelly clamp, Kocher clamp) Surgical scissors Tool for tissue cutting, dissection, and suture. Straight and curved scissors are used for cutting different structures. (e.g. Mayo scissors, Metzenbaum scissors, Pott’s scissors, Iris Scissors). Bone cutters: unpowered or powered saws, drills and pliers-like devices Needles/Sutures Tools used for suturing dissection sites or closing cuts. Needles have different shapes (e.g. j shape, ½ circle, straight) and cutting edges (tapered - round, conventional cutting - triangular) depending on the application and areas of the suture. Sutures can be categorized based on different sizes (e.g.#5-#11, higher numbers represent larger suture diameter) and types (absorbable and nonabsorbable and braided and non-braided) as well. Needle drivers(needle holders) Tools used to hold suture needle while it is passed through tissue and to grasp suture while instrument knot tying. Retractors, used to spread open skin, ribs and other tissue Tools for various purposes depending on the condition. Retractors can be used to expose incision openings, hold tissue back, or maintain operating areas. They can be categorized into either hand-held retractors or self-retaining ones (via a ratcheting mechanism) (e.g., Deaver retractor, Weitlaner retractor, Malleable Retractor). Distractors, positioners and stereotactic devices Mechanical cutters (scalpels, lancets, trocars, Harmonic scalpel, rongeurs etc.) Dilators and specula, for access to narrow passages or incisions Suction tips and tubes, for removal of bodily fluids Tools used to remove secretion, debris, or any fluid in the surgical area. (e.g. Yankauer Suction Tube, Poole Suction Tube, Frazier Suction Tip) Sealing devices, such as surgical staplers Tools used for resection (Removing part of an organ), transaction (Cutting through and sealing organs and tissues), and anastomoses (Creating connections between structures). (e.g. linear stapler, linear cutter, clips) Irrigation and injection needles, tips and tubes, for introducing fluid Powered devices, such as cranial drills and dermatomes Scopes and probes, including fiber optic endoscopes and tactile probes Carriers and appliers for optical, electronic, and mechanical devices Ultrasound tissue disruptors, cryotomes and cutting laser guides Measurement devices, such as rulers and calipers Energy systems tools are used to cut tissues or seal vesselsElectrosurgery is a modern technology that uses high frequency electrical current to cut or coagulate blood. Argon plasma coagulation involves the application of gas discharges in argon. Ultrasound surgery uses high frequency and high energy sound waves to target and destroy tissue. LigaSure fuses vessels up to 7mm in diameter in an efficient manner. Terminology The expression surgical instrumentation is somewhat interchangeably used with surgical instruments, but its meaning in medical jargon is the activity of providing assistance to a surgeon with the proper handling of surgical instruments during an operation, by a specialized professional, usually a surgical technologist or sometimes a nurse or radiographer.An important relative distinction regarding surgical instruments is the amount of bodily disruption or tissue trauma that their use might cause the patient. Terms relating to this issue are atraumatic and minimally invasive. See also Instruments used in general surgery Medical instruments and implants Gallery References External links Edgar R. McGuire Historical Medical Instrument Collection from the University at Buffalo Libraries Bibliography Wells, MP, Bradley, M: Surgical Instruments A Pocket Guide. W.B. Saunders, 1998.

Occipital neuralgia

Occipital neuralgia (ON) is a painful condition affecting the posterior head in the distributions of the greater occipital nerve (GON), lesser occipital nerve (LON), third occipital nerve (TON), or a combination of the three. It is paroxysmal, lasting from seconds to minutes, and often consists of lancinating pain that directly results from the pathology of one of these nerves. It is paramount that physicians understand the differential diagnosis for this condition and specific diagnostic criteria. There are multiple treatment modalities, several of which have well-established efficacy in treating this condition. Signs and symptoms Patients presenting with a headache originating at the posterior skull base should be evaluated for ON. This condition typically presents as a paroxysmal, lancinating or stabbing pain lasting from seconds to minutes, and therefore a continuous, aching pain likely indicates a different diagnosis. Bilateral symptoms are present in one-third of cases. Causes Occipital neuralgia is caused by damage to the occipital nerves, which can arise from trauma (usually concussive or cervical), physical stress on the nerve, repetitive neck contraction, flexion or extension, and/or as a result of medical complications (such as osteochondroma, a benign bone tumour). A rare cause is a cerebrospinal fluid leak. Rarely, occipital neuralgia may be a symptom of metastasis of certain cancers to the spine. Among other cranial neuropathies, occipital neuralgia is also known to occur in patients with multiple sclerosis. Differential diagnosis The conditions most easily mistaken with ON for other headache and facial pain disorders include migraine, cluster headache, tension headache, and hemicrania continua. Mechanical neck pain from an upper disc, facet, or musculoligamentous sources may refer to the occiput, but is not classically lancinating or otherwise neuropathic and should not be confused with ON. A crucial step in differentiating ON from other disorders is relief with an occipital nerve block. Epidemiology In one study investigating the incidence of facial pain in a Dutch population, ON comprised 8.3% of facial pain cases. The total incidence of ON was 3.2 per 100,000 people, with a mean age of diagnosis of 54.1 years. Treatment There are multiple treatment options for ON. The most conservative treatments, such as immobilization of the neck by the cervical collar, physiotherapy, and cryotherapy have not been shown to perform better than placebo. Non-steroidal anti-inflammatory drugs, tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and anticonvulsants may help to alleviate symptoms. Following diagnostic nerve blocks, therapeutic blocks may be attempted. Typically, a steroid is added to the local anesthetic with variable results. Botulinum Toxin A injection has emerged as a treatment with a conceptually lower side effect profile than many other techniques described here, with most recent trials demonstrating 50% or more improvement.It remains a common practice to utilize a landmark-only approach when performing greater and lesser occipital nerve blocks. For blockade of both nerves, medication is infiltrated along the nuchal ridge. This technique, while easy to perform and relatively safe if done correctly, may not be particularly accurate and as a result, could theoretically increase the risk of a false-positive result. To improve accuracy, ultrasound-guided techniques were developed. The original ultrasound-guided technique for injection of the GON was described by Greher and colleagues in 2010; it targets the nerve as it courses superficial to the obliquus capitis inferior muscle at the C1-C2 level.There are several advanced interventional procedures in clinical use: Pulsed or thermal radiofrequency ablation (RFA) may be considered for longer-lasting relief after a local anesthetic blockade confirms the diagnosis. Thermal RFA aimed at destroying the nerve architecture can render long-term analgesia but also comes with the potential risks of hypesthesia, dysesthesia, anesthesia dolorosa, and painful neuroma formation. Chemical neurolysis with alcohol or phenol carries the same risks as thermal RFA. There is no such risk with pulsed RF, however, some question its efficacy as compared to other procedures. Neuromodulation of the occipital nerve(s) involves the placement of nerve stimulator leads in a horizontal or oblique orientation at the base of the skull across where the greater occipital nerve emerges. Patients should be trialed with temporary leads first, and greater than 50% pain relief for several days is considered a successful trial after which permanent implantation may be considered. Risks include surgical site infection and lead or generator displacement or fracture after the operation. Ultrasound-guided percutaneous cryoablation of the GON is sometimes performed. At the correct temperature, there should be stunning but not permanent damage of the nerve, but at temperatures below negative 70 degrees Celsius, nerve injury is possible. Most recently in the literature, a 2018 article by Kastler and colleagues described 7 patients who underwent cryoneurolysis in a non-blinded fashion to good effect, but the follow-up was limited to 3 months. Surgical decompression is often considered to be the last resort. In one study of 11 patients, only two patients did not experience significant pain relief postoperatively and mean pain episodes per month decreased from 17.1 to 4.1, with mean pain intensity scores also decreasing from 7.18 to 1.73. Resection of part of the obliquus capitis inferior muscle has shown success in patients who have an exacerbation of their pain with flexion of the cervical spine. Another popular surgical technique is C2 gangliotomy, even though patients are left with several days of intermittent nausea and dizziness. As with any large nerve resection, there is a theoretical risk of developing a deafferentation syndrome, though arguably the risk is lower if the resection is pre-ganglionic. References External links Occipital Neuralgia - National Institute of Neurological Disorders and Stroke