when does the rate of venous return increase
Pulsus paradoxus


in the jugular venous pressure height (Kussmaul's sign). As is usual with inspiration, the heart rate is slightly increased, due to decreased left ventricular output. During inspiration, the negative intra-thoracic pressure results in an increased right venous return, filling the right atrium more than during an exhalation. The increased blood volume dilates the right atrium, reducing the compliance of the left atrium due to their shared septum. Lower left atrial compliance reduces the left atrium venous return and as a consequence causes a reduction in left
3631616
Venous return curve


venous return, which in turn increases left ventricular preload and stroke volume by the Frank–Starling mechanism. In this way, an increase in venous return can lead to a matched increase in cardiac output. Hemodynamically, venous return (VR) to the heart from the venous vascular beds is determined by a pressure gradient (venous pressure - right atrial pressure) and venous resistance (RV). Therefore, increases in venous pressure or decreases in right atrial pressure or venous resistance will lead to an increase in venous return, except
13178946
Bainbridge reflex


The Bainbridge reflex, also called the atrial reflex, is an increase in heart rate due to an increase in central venous pressure. Increased blood volume is detected by stretch receptors (Cardiac Receptors) located in both atria at the venoatrial junctions. Francis Arthur Bainbridge described this reflex in 1918 when he was experimenting on dogs. Bainbridge found that infusing blood or saline into the animal increased heart rate. This phenomenon occurred even if arterial blood pressure did not increase. He further observed that heart rate increased when venous pressure rose high enough
16901365
Venous return curve


Venous return is the rate of blood flow back to the heart. It normally limits cardiac output. Superposition of the cardiac function curve and venous return curve is used in one hemodynamic model. Venous return (VR) is the flow of blood back to the heart. Under steady-state conditions, venous return must equal cardiac output (Q), when averaged over time because the cardiovascular system is essentially a closed loop. Otherwise, blood would accumulate in either the systemic or pulmonary circulations. Although cardiac output and venous return
13178944
Bainbridge reflex


levels, upon which the heart rate decreases to its original level. Bainbridge Reflex is involved in Respiratory Sinus Arrhythmia. During inhalation intrathoracic pressure decreases. It triggers increased venous return which is registered by stretch receptors, which via Bainbridge Reflex increases the heart rate momentarily during inspiration. This is not to be confused with stage 4 of the Valsalva maneuver, in which the release of high intrathoracic pressure previously generated by forced expiration against a closed glottis, now restores venous return and cardiac output into a vasoconstricted circulation, stimulating the vagus nerve
16901370
Hemorheology


fluid. Contrarily, blood viscosity increases when shear rate goes down with increased vessel diameters or with low flow, such as downstream from an obstruction or in diastole. Blood viscosity also increases with increases in red cell aggregability (see below). Blood viscosity is a measure of the resistance of blood to flow. It can also be described as the thickness and stickiness of blood. This biophysical property makes it a critical determinant of friction against the vessel walls, the rate of venous return, the work required for the heart to
157014
Central venous pressure


in terms of changes in response to fluid, does not correlate with ventricular volume (i.e. preload) or volume-responsiveness, and so should not be used to guide intravenous fluid therapy. Nevertheless, CVP monitoring is a useful tool to guide hemodynamic therapy. The cardiopulmonary baroreflex responds to an increase in CVP by decreasing systemic vascular resistance while increasing heart rate and ventricular contractility in dogs. Normal CVP in patients can be measured from two points of reference: CVP can be measured by connecting the patient's central venous catheter to a
13598932
Bainbridge reflex


that the Bainbridge reflex does occur in humans, as in after delivery of an infant when a large volume (up to 800 mL) of uteroplacental blood is put back into the mother's circulation, resulting in tachycardia (citation needed). As venous return increases, the pressure in the superior and inferior vena cava increase. This results in an increase in the pressure of the right atrium, which stimulates the atrial stretch receptors (low pressure receptor zones). These receptors in turn signal the medullary control centers to increase the
16901368
Heart rate


varying rates of blood flow to the atria. Increased venous return stretches the walls of the atria where specialized baroreceptors are located. However, as the atrial baroreceptors increase their rate of firing and as they stretch due to the increased blood pressure, the cardiac center responds by increasing sympathetic stimulation and inhibiting parasympathetic stimulation to increase HR. The opposite is also true. Increased metabolic byproducts associated with increased activity, such as carbon dioxide, hydrogen ions, and lactic acid, plus falling oxygen levels, are detected by a suite of chemoreceptors
9599670
Cardiac physiology


increases, and the cardiac centers decrease sympathetic stimulation and increase parasympathetic stimulation. As pressure and stretch decrease, the rate of baroreceptor firing decreases, and the cardiac centers increase sympathetic stimulation and decrease parasympathetic stimulation. There is a similar reflex, called the atrial reflex or Bainbridge reflex, associated with varying rates of blood flow to the atria. Increased venous return stretches the walls of the atria where specialized baroreceptors are located. However, as the atrial baroreceptors increase their rate of firing and as they stretch due to the increased blood pressure
1157553
Impedance phlebography


by inflating a pneumatic cuff around the thigh to sufficient pressure to cut off venous flow but not arterial flow, causing the venous blood pressure to rise until it equals the pressure under the cuff. When the cuff is released there is a rapid venous runoff and a prompt return to the resting blood volume. Venous thrombosis will alter the normal response to temporary venous obstruction in a highly characteristic way, causing a delay in emptying of the venous system after the release of the tourniquet. The increase in blood volume after cuff inflation is
364165
Vein


Standing or sitting for a prolonged period of time can cause low venous return from venous pooling (vascular) shock. Fainting can occur but usually baroreceptors within the aortic sinuses initiate a baroreflex such that angiotensin II and norepinephrine stimulate vasoconstriction and heart rate increases to return blood flow. Neurogenic and hypovolaemic shock can also cause fainting. In these cases, the smooth muscles surrounding the veins become slack and the veins fill with the majority of the blood in the body, keeping blood away from the brain and causing unconsciousness. Jet pilots wear
8569224
Heart


blood flow to the atria. Increased venous return stretches the walls of the atria where specialized baroreceptors are located. However, as the atrial baroreceptors increase their rate of firing and as they stretch due to the increased blood pressure, the cardiac center responds by increasing sympathetic stimulation and inhibiting parasympathetic stimulation to increase heart rate. The opposite is also true. Chemoreceptors present in the carotid body or adjacent to the aorta in an aortic body respond to the blood's oxygen, carbon dioxide levels. Low oxygen or high carbon dioxide will stimulate
16207099
Deep vein thrombosis


location of DVT within the body. In isolated distal DVT, the profile of risk factors appears distinct from proximal DVT. Transient factors, such as surgery and immobilization, appear to dominate, whereas thrombophilias and age do not seem to increase risk. In upper-extremity DVT, the most important risk factor is having a central venous catheter, and thoracic outlet syndrome also increases risk. DVT often develops in the calf veins and "grows" in the direction of venous flow, towards the heart. When DVT does not grow
12296887
Orthostatic syncope


extremities, splanchnic and pulmonary circulations. The decrease in venous return to the heart reduces cardiac output and eventually causes a drop in blood pressure. Baroreceptors in the carotid and aortic arteries sense this decrease in blood pressure and activate the sympathetic nervous system which leads to increased heart rate, systemic vasoconstriction, and increased cardiac muscle contractility all of which eventually increase blood pressure. In a healthy individual, this sympathetic activation causes a physiological increase in heart rate by 10 to 20 bpm, diastolic blood pressure by 5mmHg, but minimal to no
719411
Diosmin


venous capacitance, distensibility, and venous stasis. This increases the venous return and reduces venous hyperpressure present in patients suffering from CVI. Diosmin improves lymphatic drainage by increasing the frequency and intensity of lymphatic contractions, and by increasing the total number of functional lymphatic capillaries. Furthermore, diosmin with hesperidine decreases the diameter of lymphatic capillaries and the intralymphatic pressure. At the microcirculation level, diosmin reduces capillary hyperpermeability and increases capillary resistance by protecting the microcirculation from damaging processes. Diosmin reduces the expression of endothelial adhesion molecules (ICAM1, VCAM1)
10765183
Vagal tone


blood flow to the heart, which in turn triggers baroreceptors which act to diminish vagal tone. This causes an increase in heart rate. During exhalation, the diaphragm relaxes, moving upward, and decreases the size of the chest cavity, causing an increase in intrathoracic pressure. This increase in pressure inhibits venous return to the heart resulting in both reduced atrial expansion and reduced activation of baroreceptors. This relieves the suppression of vagal tone and leads to a decreased heart rate. RSA is frequently used as a noninvasive method for investigating vagal
8859093
Blood pressure


central blood volume and a reduction of ventricular preload which in turn reduces stroke volume, and mean arterial pressure. Normally this is compensated for by multiple mechanisms, including activation of the autonomic nervous system which increases heart rate, myocardial contractility and systemic arterial vasoconstriction to preserve blood pressure and elicits venous vasoconstriction to decrease venous compliance. Decreased venous compliance also results from an intrinsic myogenic increase in venous smooth muscle tone in response to the elevated pressure in the veins of the lower body. Other compensatory mechanisms include the veno-arteriolar axon reflex
11702681
Bainbridge reflex


heart rate (Tachycardia). Unusually, this tachycardia is mediated by increased sympathetic activity to the sinoatrial node (SAN) with no fall in parasympathetic activity. Increasing the heart rate serves to decrease the pressure in the superior and inferior venae cavae by drawing more blood out of the right atrium. This results in a decrease in atrial pressure, which serves to bring in more blood from the vena cavae, resulting in a decrease in the venous pressure of the great veins. This continues until right atrial blood pressure returns to normal
16901369
Cardiac physiology


stretch of the ventricle the greater the contraction. Any sympathetic stimulation to the venous system will increase venous return to the heart and ventricular filling. The ventricles must develop a certain tension to pump blood against the resistance of the vascular system. This tension is called afterload. When the resistance is increased particularly due to stenotic valve damage the afterload must necessarily increase. A decrease in normal vascular resistance can also occur. Different cardiac responses operate to restore homeostasis of the pressure and blood flow. The ability of the myocardium to contract,
1157560
Accelerans nerve


The heart beats according to a rhythm set up by the sinus node or pacemaker. It is acted on by the nervous system, as well as hormones in the blood, and venous return: the amount of blood being returned to the heart. The two nerves acting on the heart are the vagus nerve, which slows heart rate down by emitting acetylcholine, and the accelerans nerve which speeds it up by emitting noradrenaline. This results in an increased bloodflow, preparing the body for a sudden increase in activity. These nerve fibers
7533739
Chronic wound pain


foot ulcers, pressure ulcers, malignancy, infection, inflammation and stress are associated with chronic wound pain. Venous leg ulcers are commonly associated with chronic wound pain. The pain prevalence rate for venous leg ulcers is 50-87%. The pain experienced with venous leg ulcers may be constant, or intermittent varying in intensity. Venous leg ulcers may cause nociceptive and neuropathic pain, and ultimately be expressed as persistent background pain. Venous leg ulceration is due to poor venous return and venous hypertension as resulting from venous reflux or obstruction.1
21465136
Amrinone


capillary wedge pressure while increasing cardiac output because it functions as an arterial vasodilator and increases venous capacitance while decreasing venous return. There is a net decrease in myocardial wall tension, and O consumption when using amrinone. Amrinone also has beneficial effects during diastole in the left ventricle including relaxation, compliance and filling in patients with congestive heart failure. Short-term management of severe CHF (not used long term because of increased mortality, probably due to heart failure). Congestive heart failure (CHF) is characterized by a reduction in
3802958
Bainbridge reflex


to distend the right atrium, but denervation of the vagi to the heart eliminated these effects. Increased blood volume results in increased venous return to the heart, which leads to increased firing of B-fibers. B-fibers send signals to the brain (the afferent pathway of the neural portion of the Bainbridge reflex), which then modulates both sympathetic and parasympathetic pathways to the SA node of the heart (the efferent pathway of the neural portion of the Bainbridge reflex), causing an increase in heart rate. "Effects
16901366
Compression stockings


deoxygenated blood back to the heart. Varicose veins are saccular and distended veins which can expand considerably and may cause painful venous inflammation. Once developed, they will not disappear on their own. The formation of varicose veins is an externally visible sign of venous weakness. Deep vein thrombosis occurs when blood flow decreases (especially in the lower extremities), causing blood to pool in the legs and leading to blood clot (thrombus) formation. Evidence does not suggest a benefit in post thrombotic syndrome rates following DVT. Compression stockings are
6830370
Passive leg raise


so that adequate volume of blood will return to the right heart during the maneuver. The physiology of assessing fluid responsiveness via passive leg raise requires increasing systemic venous return without altering cardiac function - a form of functional hemodynamic monitoring. Several studies showed that this measure is a better predictor of response to rapid fluid loading than other tests such as respiratory variation in pulse pressure or echocardiographic markers. Placing the person in the Trendelenburg position, does not work since bloodvessels are highly compliant, and expand as result of the increased volume locally.
11233936
Dydrogesterone


cancer is non-significantly higher with dydrogesterone). Similarly, like oral progesterone but in contrast to other progestins, dydrogesterone does not appear to further increase the risk of venous thromboembolism when used in combination with an oral estrogen. However, as with oral progesterone, dydrogesterone offers inferior endometrial protection relative to other progestogens such as medroxyprogesterone acetate and norethisterone acetate, with a significantly increased risk of endometrial cancer in combination with an estrogen with long-term therapy (5 years). Dydrogesterone does not bind importantly to the androgen, estrogen
20561148
Skeletal-muscle pump


The skeletal-muscle pump is a collection of skeletal muscles that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart, but may also play a role in arterial blood flow. The skeletal pump is vital in negating orthostatic intolerance when standing. When moving upright, the blood volume moves to the peripheral parts of the body. To combat this the muscles involved in standing contract and help to bring venous blood volume to the heart. The pump is important in affecting the central
18736898
Venous ulcer


as current evidence would not support this approach as standard care. EVRA (Early Venous Reflux Ablation) ulcer trial – A UK NIHR HTA funded randomised clinical trial to compare early versus delayed endovenous treatment of superficial venous reflux in patients with chronic venous ulceration opened for recruitment in October 2013. The study hopes to show an increase in healing rates from 60% to 75% at 24 weeks. Research from the University of Surrey and funded by the Leg Ulcer Charity is currently looking at the psychological impact of having a leg ulcer,
782322
Venous return curve


are interdependent, each can be independently regulated. The circulatory system is made up of two circulations (pulmonary and systemic) situated in series between the right ventricle (RV) and left ventricle (LV). Balance is achieved, in large part, by the Frank–Starling mechanism. For example, if systemic venous return is suddenly increased (e.g., changing from upright to supine position), right ventricular preload increases leading to an increase in stroke volume and pulmonary blood flow. The left ventricle experiences an increase in pulmonary
13178945
Anorectal varices


rectal vein and via the inferior mesenteric vein to the liver as part of the portal venous system. Blood from the middle and inferior portions of the rectum is drained via the middle and inferior rectal veins. In portal hypertension, venous resistance is increased within the portal venous system; when the pressure in the portal venous system increases above that of the systemic, blood is shunted through the portosystemic anastomoses. The shunting of blood and consequential increase of pressure through the collateral veins causes the varicosities. The terms rectal varices and haemorrhoids are
6244107
Venous ulcer


vascular service" for venous duplex ultrasound and assessment for endovenous surgery. Signs and symptoms of venous ulcers include: The exact cause of venous ulcers is not certain, but they are thought to arise when venous valves that exist to prevent backflow of blood do not function properly, causing the pressure in veins to increase. The body needs the pressure gradient between arteries and veins in order for the heart to pump blood forward through arteries and into veins. When venous hypertension exists, arteries no longer have significantly higher pressure than veins,
782304
Stroke volume


or speed of venous return will increase preload and, through the Frank–Starling law of the heart, will increase stroke volume. Decreased venous return has the opposite effect, causing a reduction in stroke volume. Elevated afterload (commonly measured as the aortic pressure during systole) reduces stroke volume. Though not usually affecting stroke volume in healthy individuals, increased afterload will hinder the ventricles in ejecting blood, causing reduced stroke volume. Increased afterload may be found in aortic stenosis and arterial hypertension. Similar to cardiac index, is a
15157204
Central venous pressure


be graphically depicted as changes in the slope of the venous return plotted against right atrial pressure (where central venous pressure increases, but right atrial pressure stays the same; VR = CVP − RAP). CVP has been, and often still is, used as a surrogate for preload, and changes in CVP in response to infusions of intravenous fluid have been used to predict volume-responsiveness (i.e. whether more fluid will improve cardiac output). However, there is increasing evidence that CVP, whether as an absolute value or
13598931
Macula densa


decrease reabsorption of ions and water to the blood (as needed) in order to alter blood volume and return blood pressure to normal. A decrease in afferent arteriole diameter causes a decrease in the GFR (glomerular filtration rate), resulting in a decreased concentration of sodium and chloride ions in the filtrate and/or decreased filtrate flow rate. Reduced blood pressure means decreased venous pressure and, hence, a decreased peritubular capillary pressure. This results in a smaller capillary hydrostatic pressure, which causes an increased absorption of sodium ions into the vasa
10332249
Etilefrine


Etilefrine is a cardiac stimulant used as an antihypotensive. It is a sympathomimetic amine of the 3-hydroxy-phenylethanolamine series used in treating orthostatic hypotension of neurological, cardiovascular, endocrine or metabolic origin. Intravenous infusion of this compound increases cardiac output, stroke volume, venous return and blood pressure in man and experimental animals, suggesting stimulation of both α and β adrenergic receptors. However, "in vitro" studies indicate that etilefrine has a much higher affinity for β (cardiac) than for β adrenoreceptors. Intravenous etilefrine increases the pulse rate
9029389
Blood


min to the body. In a healthy adult at rest, oxygen consumption is approximately 200–250 ml/min, and deoxygenated blood returning to the lungs is still roughly 75% (70 to 78%) saturated. Increased oxygen consumption during sustained exercise reduces the oxygen saturation of venous blood, which can reach less than 15% in a trained athlete; although breathing rate and blood flow increase to compensate, oxygen saturation in arterial blood can drop to 95% or less under these conditions. Oxygen saturation this low is considered dangerous
3594549
Constriction


with neural processing and damage tissues at high pressures. During constriction events where the prey's heart is impeded, arterial pressure drops while venous pressure increases, and blood vessels begin to close. The heart does not have enough strength to pump against the pressure and blood flow stops. Internal organs with high metabolic rates, including the brain, liver, and heart, begin to stop functioning and die due to ischemia, a loss of oxygen and glucose. There is evidence that boa constrictors have more difficulty killing ectotherms—animals like
12781986
Medroxyprogesterone acetate


in women. DMPA can affect menstrual bleeding. After a year of use, 55% of women experience amenorrhea (missed periods); after 2 years, the rate rises to 68%. In the first months of use "irregular or unpredictable bleeding or spotting, or, rarely, heavy or continuous bleeding" was reported. MPA does not appear to be associated with vitamin B12 deficiency. A 2.2- to 3.6-fold greater rate of venous thromboembolism has been observed when DMPA is used as birth control in premenopausal women. However,
13913530
Skeletal-muscle pump


and local supply of blood output. Venous return, cardiac output, and stroke volume were all increased during exercise experiments, as well as affecting the local muscle being used, blood volume. Between muscle relaxations intramuscular pressure transiently returns to a level below the venous blood pressure and blood from the capillary system refills the veins until the next contraction. It is postulated that this change in pressure may be great enough to draw blood from the arterial side to the venous side. It is hypothesized that this pressure drop during rhythmic contraction actually
18736899
Idiopathic intracranial hypertension


(flattening of the pituitary gland due to increased pressure) and enlargement of Meckel's caves may be seen. An MR venogram is also performed in most cases to exclude the possibility of venous sinus stenosis/obstruction or cerebral venous sinus thrombosis. A contrast-enhanced MRV (ATECO) scan has a high detection rate for abnormal transverse sinus stenoses. These stenoses can be more adequately identified and assessed with catheter cerebral venography and manometry. Buckling of the bilateral optic nerves with increased perineural fluid is also often noted on MRI imaging.
5302314
Heart murmur


the left upper sternal border, associated with a systolic ejection click that increases with inspiration (due to increased venous return to the right side of the heart) and sometimes radiates to the left clavicle. Tricuspid valve regurgitation presents as a holosystolic (pansystolic) murmur at the left lower sternal border with radiation to the left upper sternal border. Prominent v and c waves may be seen in the JVP (jugular venous pressure). The murmur will increase with inspiration. Hypertrophic obstructive cardiomyopathy (or hypertrophic subaortic stenosis) will be a
9370893
Photoplethysmogram


decreases by up to 4 mm Hg, which distends the right atrium, allowing for faster filling from the vena cava, increasing ventricular preload, but decreasing stroke volume. Conversely during expiration, the heart is compressed, decreasing cardiac efficiency and increasing stroke volume. When the frequency and depth of respiration increases, the venous return increases, leading to increased cardiac output. Anesthesiologists must often judge subjectively whether a patient is sufficiently anesthetized for surgery. As seen in the figure, if a patient is not sufficiently anesthetized, the sympathetic nervous
11545321
Testicular torsion


increased risk. Testicular torsion occurs when there is mechanical twisting of the spermatic cord, which suspends the testicle within the scrotum and contains the testicular artery and vein. Twisting of the cord reduces or eliminates blood flow to the testicle. The degree of arterial and venous obstruction depends on the duration and severity of the torsion event. Typically, venous blood flow is compromised first. The increase in venous pressure subsequently causes decreased arterial blood flow, leading to decreased oxygen supply to the testicle, and if untreated, testicular infarction. It
3078603
Tricuspid insufficiency


Tricuspid insufficiency (TI), more commonly called tricuspid regurgitation (TR), is a type of valvular heart disease in which the tricuspid valve of the heart, located between the right atrium and right ventricle, does not close completely when the right ventricle contracts (systole). TR allows the blood to flow backwards from the right ventricle to the right atrium, which increases the volume and pressure of the blood both in the right atrium and the right ventricle, which may increase central venous volume and pressure if the backward flow
16723011
Hypertension


the number or density of capillaries may also contribute. It is not clear whether or not vasoconstriction of arteriolar blood vessels plays a role in hypertension. Hypertension is also associated with decreased peripheral venous compliance which may increase venous return, increase cardiac preload and, ultimately, cause diastolic dysfunction. Pulse pressure (the difference between systolic and diastolic blood pressure) is frequently increased in older people with hypertension. This can mean that systolic pressure is abnormally high, but diastolic pressure may be normal or low, a condition termed isolated systolic hypertension
1126408
Breathing


carbon dioxide by the active muscles. This carbon dioxide diffuses into the venous blood and ultimately raises the partial pressure of carbon dioxide in the arterial blood. This is immediately sensed by the carbon dioxide chemoreceptors on the brain stem. The respiratory centers respond to this information by causing the rate and depth of breathing to increase to such an extent that the partial pressures of carbon dioxide and oxygen in the arterial blood return almost immediately to the same levels as at rest. The respiratory centers communicate with the muscles of breathing via motor nerves
21663320
Pressure–volume loop analysis in cardiology


decreases the afterload. Preload is described as the stretching of a single cardiac myocyte immediately prior to contraction and is, therefore, related to the sarcomere length. Since sarcomere length cannot be determined in the intact heart, other indices of preload such as ventricular end-diastolic volume or pressure are used. As an example, preload increases when venous return is increased. This is because the end-diastolic pressure and volume of the ventricle are increased, which stretches the sarcomeres. Preload can be calculated as where Stroke volume (
7257790
Frank–Starling law


end-diastolic volume of the left and right ventricles as determined by complexities of the force-sarcomere length relationship. Due to the intrinsic property of myocardium that is responsible for the Frank-Starling mechanism, the heart can automatically accommodate an increase in venous return, at any heart rate. The mechanism is of functional importance because it serves to adapt left ventricular output to right ventricular output. If this mechanism did not exist and the right and left cardiac outputs were not equivalent, blood would accumulate in the pulmonary circulation (were
18736277
Venous return curve


when changes are brought about by altered body posture. Although the above relationship is true for the hemodynamic factors that determine the flow of blood from the veins back to the heart, it is important not to lose sight of the fact that blood flow through the entire systemic circulation represents both the cardiac output and the venous return, which are equal in the steady-state because the circulatory system is closed. Therefore, one could just as well say that venous return is determined by the mean aortic pressure minus the mean right atrial
13178947
Platypnea


or an anatomical cardiovascular defect increasing positional right-to-left shunting (bloodflow from the right to the left part of the circulatory system) such as a patent foramen ovale. These defects include rare syndromes in which the venous blood from the liver does not pass through the lungs, or if venous blood from the portal circulation reaches the inferior vena cava without passing through the liver (Abernethy malformation, type 1). The word "platypnea" uses combining forms of "platy-" + "-pnea", from Greek "
15270358
Homeostasis


limb veins are tightly constricted, not only reducing heat loss from this source, but also forcing the venous blood into the counter-current system in the depths of the limbs. The metabolic rate is increased, initially by non-shivering thermogenesis, followed by shivering thermogenesis if the earlier reactions are insufficient to correct the hypothermia. When core temperature rises are detected by thermoreceptors, the sweat glands in the skin are stimulated via cholinergic sympathetic nerves to secrete sweat onto the skin, which, when it evaporates, cools the skin and
14250512
Stasis dermatitis


Stasis dermatitis refers to the skin changes that occur in the leg as a result of "stasis" or blood pooling from insufficient venous return; the alternative name of varicose eczema comes from a common cause of this being varicose veins. Insufficient venous return results in increased pressure in the capillaries with the result that both fluid and cells may "leak" out of the capillaries. This results in red cells breaking down, with iron containing hemosiderin possibly contributing to the pathology of this entity. The cracks and poor skin-condition of
10621340
Venous thrombosis


non-surgical patients, mortality does not appear to change. It does not appear, however, to decrease the rate of symptomatic DVTs. Using both heparin and compression stockings appears better than either one alone in reducing the rate of DVT. In hospitalized people who have had a stroke and not had surgery, mechanical measures (compression stockings) resulted in skin damage and no clinical improvement. Data on the effectiveness of compression stockings among hospitalized non-surgical patients without stroke is scarce. The American College of Physicians (ACP)
1275666
Anomalous pulmonary venous connection


Anomalous pulmonary venous connection (or anomalous pulmonary venous drainage or anomalous pulmonary venous return) is a congenital defect of the pulmonary veins. "Total anomalous pulmonary venous connection", also known as total "anomalous pulmonary venous return", is a rare cyanotic congenital heart defect in which all four pulmonary veins are malpositioned and make anomalous connections to the systemic venous circulation. (Normally, pulmonary veins return oxygenated blood from the lungs to the left atrium where it can then be pumped to the rest of the body). A patent
1211432
Fat embolism syndrome


, there is no difference in mortality, infection, and avascular necrosis when compared to the control group. However, a randomised trial conducted in 2004 reported no differences in FES incidence when comparing treatment with the control group. Administration of corticosteriods for 2 to 3 days is not associated with increased rates of infection. However, there is insufficient data to support the use of methyprednisolone once FES is established. Heparin has been used in the prevention of venous thrombosis in post-operative patients; however its regular use in those with FES
4702047
Atrial natriuretic peptide receptor


bind ANP released as a result of increasing right atrial pressure and will cause the walls of the vasculature to relax. This relaxation will decrease total peripheral resistance, which will in turn decrease venous return to the heart. The decrease in venous return to the heart will reduce the preload and will result in the heart's having to do less work. There is also a soluble guanylyl cyclase that cannot be stimulated by ANP. Instead, vascular endothelial cells will use L-arginine to make nitric oxide via nitric oxide synthase.
1703679
Pulsus paradoxus


pressure on the veins, particularly the venae cavae. However, the decrease in intra-thoracic pressure and stretching of the lungs during inhalation also expands the compliant pulmonary vasculature so that blood pools in the lungs and decreases pulmonary venous return to the left atrium. Also, the increased systemic venous return to the right side of the heart expands the right heart and directly compromises filling of the left side of the heart by slightly bulging the septum to the left, reducing maximum volume. Reduced left-heart filling leads to a reduced
3631618
Femoral canal


entrance to the femoral canal is the femoral ring, through which bowel can sometimes enter, causing a femoral hernia. Though femoral hernias are rare, their passage through the inflexible femoral ring puts them at particular risk of strangulation, giving them surgical priority. The position of the femoral canal medially to the femoral vein is of physiologic importance. The space of the canal allows for the expansion of the femoral vein when venous return from the lower limbs is increased or when increased intra-abdominal pressure (valsalva maneuver) causes a temporary
15698748
Breathalyzer


producing false positives. During the initial absorption phase, arterial blood alcohol concentrations are higher than venous. After absorption, venous blood is higher. This is especially true with bolus dosing (Canadian term). With additional doses of alcohol, the body can reach a sustained equilibrium when absorption and elimination are proportional, calculating a general absorption rate of 0.02/drink and a general elimination rate of 0.015/hour. (One drink is equal to of liquor, of beer, or of wine.) Breath alcohol is a representation
20103832
Hypercoagulability in pregnancy


for reasons other than delivery or venous thromboembolism. Pregnancy after the age of 35 augments the risk of VTE, as does multigravidity of more than four pregnancies. Pregnancy in itself causes approximately a five-fold increased risk of deep venous thrombosis. Several pregnancy complications, such as pre-eclampsia, cause substantial hypercoagulability. Hypercoagulability states as a pre-existing condition in pregnancy include both acquired ones, such as antiphospholipid antibodies, and congenital ones, including factor V Leiden, prothrombin mutation, proteins C and S deficiencies, and antithrombin
13483389
Cerebral venous sinus thrombosis


rate falls and the patient assumes an abnormal posture. Cerebral venous sinus thrombosis is more common in particular situations. 85% of people have at least one of these risk factors: The diagnosis may be suspected on the basis of the symptoms, for example the combination of headache, signs of raised intracranial pressure and focal neurological abnormalities, or when alternative causes of headache and neurological abnormalities, such as a subarachnoid hemorrhage, have been excluded. There are various neuroimaging investigations that may detect cerebral sinus thrombosis. Cerebral edema and venous infarction
19919446
Combined oral contraceptive pill


contraceptives containing levonorgestrel (LNG), and with the same dose of estrogen and duration of use, the rate ratio of deep venous thrombosis for combined oral contraceptives with norethisterone is 0.98, with norgestimate 1.19, with desogestrel (DSG) 1.82, with gestodene 1.86, with drospirenone (DRSP) 1.64, and with cyproterone acetate 1.88. In comparison, venous thromboembolism occurs in 100–200 per 100.000 pregnant women every year. One study showed more than a 600% increased risk of blood clots for women taking COCPs with drospirenone compared with non
2647837
Preload (cardiology)


a surrogate for preload. Quantitatively, preload can be calculated as where: LVEDP = Left ventricular end diastolic pressure LVEDR = Left ventricular end diastolic radius (at the ventricle's midpoint) h = thickness of the ventricle. This calculation is based on the Law of Laplace which states that (wall stress) = formula_2. Hence, "preload" is the "wall stress". Preload is measured in pressure units (mm Hg). Preload is affected by venous blood pressure and the rate of venous return. These are
5154207
Quantium Medical Cardiac Output


more strength of contraction and quantity of blood pumped by the left-ventricle to the aorta. When the heart reaches a physiological limitation, then blood pumping cannot increase, although the venous return is further increased. The SVV contributes to know the state of volemia in ventilated patients and designates the point on the Frank-Starling curve where the patient is. In addition to cardiac function, the qCO also evaluates indirectly other related field as is the Parasympathetic Nervous System (PNS), through the evaluation of the R-R
20148531
Venous thrombosis


the superficial veins and, for this reason this pathology is called thrombophlebitis. The inflammatory reaction and the white blood cells play a role in the resolution of venous clots. The initial treatment for venous thromboembolism is typically with either low molecular weight heparin (LMWH) or unfractionated heparin. LMWH appears to have lower rates of side effects; however, both result in similar rates of survival. Superficial venous thromboses cause discomfort but generally not serious consequences, as do the deep vein thromboses (DVTs) that form in the deep veins of
1275656
Hysterical strength


vehicles to rescue their children, and when people are in life-and-death situations. Hysterical strength can result in torn muscles due to higher mechanical stress. Early experiments showed that adrenaline increases twitch, but not tetanic force and rate of force development in muscles. It is questionable, however, as to whether adrenaline, released from the adrenal medulla into the venous circulation, can reach the muscle quickly enough in order to be able to cause such an effect in the midst of a crisis. It may be that noradrenaline
22002113
Compression stockings


Compression stockings are a specialized hosiery designed to help prevent the occurrence of, and guard against further progression of, venous disorders such as edema, phlebitis and thrombosis. Compression stockings are elastic garments worn around the leg, compressing the limb. This reduces the diameter of distended veins and increases venous blood flow velocity and valve effectiveness. Compression therapy helps decrease venous pressure, prevents venous stasis and impairments of venous walls, and relieves heavy and aching legs. Knee-high compression stockings are used not only to help increase circulation, but
6830367
Common raven physiology


avoid hyperthermia. In response, the common raven experiences an increased heart rate and cardiac output. Another method used by many species of birds to regulate thermal conductance is by internally adjusting blood flow through shunt vessels. More specifically, arterial and venous blood vessels are organized to bypass the countercurrent heat exchange occurring in the upper portion of a bird’s legs. Countercurrent heat exchange involves arrangements of blood vessels that allow heat to transfer from warm arterial blood to cooler venous blood travelling to the body’s core. Through this mechanism, arterial
13321493
Passive leg raise


gravity to pull blood from the legs, thus increasing circulatory volume available to the heart (cardiac preload) by around 150-300 milliliters, depending on the amount of venous reservoir. The real-time effects of this maneuver on hemodynamic parameters such as blood pressure and heart rate are used to guide the decision whether or not more fluid will be beneficial. The assessment is easier when invasive monitoring is present (such as an arterial catheter). The maneuver might be reinforced in a clinical setting by moving the patient's bed
11233933
Altitude sickness


The hypoxia leads to an increase in minute ventilation (hence both low CO, and subsequently bicarbonate), Hb increases through haemoconcentration and erythrogenesis. Alkylosis shifts the haemaglobin dissociation constant to the left, 2,3-DPG increases to counter this. Cardiac output increases through an increase in heart rate. The body's response to high altitude includes the following: People with high-altitude sickness generally have reduced hyperventilator response, impaired gas exchange, fluid retention or increased sympathetic drive. There is thought to be an increase in cerebral venous volume because of
1126729
Ultrasonography of chronic venous insufficiency of the legs


the superficial veins belonging to compartment N3 very rarely become sinuous. So that when a sinuous vein is detected, the sonographer will suspect that it is a tributary. The sapheno-femoral junction is tested by the Valsalva maneuver with the use of color Doppler being helpful at this stage. The wall thickness of the vein is significantly increased in venous reflux, being approximately 0.58 mm in venous reflux, compared to up to 0.45 mm normally. The accessory saphenous vein (ASV), either anterior or posterior, is an important GSV
6594979
Pulmonary contusion


prevent shock without exacerbating edema. Diuretics, drugs that increase urine output to reduce excessive fluid in the system, can be used when fluid overload does occur, as long as there is not a significant risk of shock. Furosemide, a diuretic used in the treatment of pulmonary contusion, also relaxes the smooth muscle in the veins of the lungs, thereby decreasing pulmonary venous resistance and reducing the pressure in the pulmonary capillaries. Retaining secretions in the airways can worsen hypoxia and lead to infections. Thus, an important part of treatment
1091175
D-dimer


It has therefore been suggested to use a cutoff equal to patient’s age in years × 10 µg/L (or x 0.056 nmol/L) for patients aged over 50 years for the suspicion of venous thromboembolism (VTE), as it decreases the false positive rate without substantially increasing the false negative rate. Various kits have a 93-95% sensitivity (true positive rate). For hospitalized patients, one study found the specificity to be about 50% (related to false positive rate) in the diagnosis of
6258896
Ileal interposition


mechanism 5) Increased gastric emptying and decreased ghrelin levels 6) Regulation of late phase insufficient glucagon suppression 7) Reduction of increased hepatic glucose output 8) Resolution / control of type 2 diabetes and accompanying co-morbidities Complication Rates = %4 - 6,5 Mortality Rates= %0,1-0,27 Infection: %0,4 - 0,55 Venous Thromboembolism: %0,1 - 0,27 Hemorrhage: %11,8 Hernia: Unreported Bowel obstruction: %0,3-0,5 Technical Complications: Anastomosis Leak: %1 - 2,2 Narrowness: %1 - 1,4 Ulceration: %0,8
22027925
Capillary


explicitly predict the existence of capillaries, but he clearly saw the need for some sort of connection between the arterial and venous systems. He wrote, "…the blood doth enter into every member through the arteries, and does return by the veins, and that the veins are the vessels and ways by which the blood is returned to the heart itself; and that the blood in the members and extremities does pass from the arteries into the veins (either mediately by an anastomosis, or immediately through the porosities of the flesh
11702239
Pulmonary heart disease


is present, the majority of individuals require a bronchodilator. A variety of medications have been developed to relax the blood vessels in the lung, calcium channel blockers are used but only work in few cases and according to NICE are not recommended for use at all. Anticoagulants are used when venous thromboembolism is present. Venesection is used in severe secondary polycythemia (because of hypoxia), which improves symptoms though survival rate has not been proven to increase. Finally, transplantation of single/double lung in extreme cases of cor pulmonale is
6954275
Postural orthostatic tachycardia syndrome


it may promote supine hypertension. Ivabradine can successfully restrain heart rate in POTS without affecting blood pressure and approximately 60% of people with POTS treated in an open-label trial of ivabradine experienced symptom improvement. Pyridostigmine has been reported to restrain heart rate and improve chronic symptoms in about half of people. The selective alpha 1 agonist phenylephrine has been used successfully to enhance venous return and stroke volume in some people with POTS. However, this medication may be hampered by poor oral bioavailability. POTS has a favorable prognosis when managed appropriately
3211857
Risk arbitrage


and 1996, experienced a break rate of 22.7%. Several authors find that the returns to risk arbitrage are somewhat uncorrelated to the returns of the stock market in typical market environments. However, risk arbitrage is not necessarily insensitive to the performance of the stock market in all market conditions. When the stock market experiences a decrease of 4% or more, the beta (finance) between merger arbitrage returns and risk arbitrage returns can increase to 0.5. This suggests that the exposure to market risk is asymmetric: the arbitrageur does
4064248
Penalized present value


The Penalized Present Value (PPV) is a method of Capital Budgeting under risk developed by Fernando Gómez-Bezares in the 1980s. The risk-adjusted rate of return method penalizes risk by increasing the discount rate when calculating the Net Present Value (NPV), and the certainty equivalent approach does it by adjusting the numerators of the NPV formula, while the Penalized Present Value calculates the average NPV (µ) at the risk-free rate, penalizing it afterwards by subtracting t standard deviations of the NPV (tσ):
6580053
Hypoxemia


. In general, a shunt may be within the heart or lungs, and cannot be corrected by administering oxygen alone. Shunting may occur in normal states: Shunting may also occur in disease states: Exercise-induced arterial hypoxemia occurs during exercise when a trained individual exhibits an arterial oxygen saturation below 93%. It occurs in fit, healthy individuals of varying ages and genders. Adaptations due to training include an increased cardiac output from cardiac hypertrophy, improved venous return, and metabolic vasodilation of muscles, and an increased VO
7835420
Progesterone (medication)


concentrations of progesterone in the uterus that are likely fully sufficient for endometrial protection. Whereas the combination of an estrogen and a progestin is associated with an increased risk of venous thromboembolism relative to estrogen alone, there is no further increase in the risk of venous thromboembolism with the combination of an estrogen and oral progesterone relative to estrogen only. In addition, the combination of transdermal estradiol with oral progesterone is not associated with any increased risk of venous thromboembolism ( = 0.93). The reasons for these differences between progesterone and progestins are not
2800612
Austerity


reduce or 'crowd out' private investment, reducing growth. This theory explains why large and sustained government deficits take a toll on growth: they reduce capital formation. But this argument rests on how government deficits affect interest rates, and the relationship between government deficits and interest rates varies. When there is considerable excess capacity, an increase in government borrowing to finance an increase in the deficit does not lead to higher interest rates and does not crowd out private investment. Instead, the higher demand resulting from the increase in the
11480175
Cardiac catheterization


a marker, the oxygen saturation of blood can be sampled at various locations in and around the heart. For example, a left-to-right atrial septal defect will show a marked increase in oxygen saturation in the right atrium, ventricle, and pulmonary artery as compared to the mixed venous oxygen saturation from the oxygenated blood from the lungs mixing into the venous return to the heart. Utilizing the Fick principle, the ratio of blood flow in the lungs (Qp) and system circulations (Qs) can calculate the Qp
784038
Venous return curve


pressure, divided by the resistance of the entire systemic circulation (i.e., the systemic vascular resistance). It is often suggested that venous return dictates cardiac output, effected through the Frank Starling mechanism. However, as noted above it is clear that, equally, cardiac output must dictate venous return since over any period of time both must necessarily be equal. Similarly, the concept of mean systemic filling pressure, the hypothetical driving pressure for venous return, is difficult to localise and impossible to measure in the physiological state. Furthermore
13178948
Gastric bypass surgery


prevent venous thromboembolic disease may actually increase the risk of hemorrhage slightly. A hernia is an abnormal opening, either within the abdomen or through the abdominal wall muscles. An internal hernia may result from surgery and re-arrangement of the bowel, and is a cause of bowel obstruction. Antecolic antegastric Roux-en-Y gastric bypass surgery has been estimated to result in internal hernia in 0.2% of cases, mainly through Petersen's defect. An incisional hernia occurs when a surgical incision does not heal well; the muscles of
4945422
Venous stasis


Venous stasis, is a condition of slow blood flow in the veins, usually of the legs. Venous stasis is a risk factor for forming blood clots in veins (venous thrombosis), as with the deep veins of the legs (deep vein thrombosis or DVT). Causes of venous stasis include long periods of immobility that can be encountered from driving, flying, bed rest/hospitalization, or having an orthopedic cast. Recommendations by clinicians to reduce venous stasis and DVT/PE often encourage increasing walking, calf exercises,
21235279
Venous ulcer


98% in a selected group of venous leg ulcers. It is not certain which dressings and topical agents are most effective for healing venous leg ulcers. Silver-containing dressings may increase the probability of healing for venous leg ulcers. A clinical trial was successfully performed with a mixture of 60% sugar or glucose powder and 40% vaseline. Venous ulcers are costly to treat, and there is a significant chance that they will recur after healing; one study found that up to 48% of venous ulcers had recurred by the
782320
Southern bluefin tuna


this species of tuna has developed a shunting system. When the southern bluefin tuna experiences cold temperatures, more blood is directed to the rete vascular system, heating muscle tissue, while in warm temperatures, blood is shunted to the venous and arterial systems, reducing the heat in the muscle tissues. The tuna's heart must pump blood to the bodily extremities at a quick rate to conserve heat and reduce heat loss. The heart of tunas is able to adapt to colder water temperatures, mainly by increasing blood flow and pumping warm
10723142
Mitral valve stenosis


. Rolling the patient toward left as well as isometric exercise will accentuate the murmur. A thrill might be present when palpating at the apical region of the precordium. Advanced disease may present with signs of right-sided heart failure such as parasternal heave, jugular venous distension, hepatomegaly, ascites and/or pulmonary hypertension, the latter often presenting with a loud P. Almost all signs increase with exercise and pregnancy. Other peripheral signs include: Medical signs of atrial fibrillation include: Heart rate is about 100-150/min. Irregularly irregular
5316651
Phenylephrine


of this, it should be given through a central line if at all possible. Damage may be prevented or mitigated by infiltrating the tissue with the alpha blocker phentolamine by subcutaneous injection. Phenylephrine hydrochloride at 0.25% is used as a vasoconstrictor in some suppository formulations. Recently, Phenylephrine has been used to treat conditions of orthostatic intolerance such as Postural Orthostatic Tachycardia Syndrome - where by activation of venous alpha 1 adrenoreceptors increases venous return and stroke volume which improves symptoms. Phenylephrine is used to treat priapism. It is diluted with normal saline
12248202
Right atrial pressure


Right atrial pressure (RAP) is the blood pressure in the right atrium of the heart. RAP reflects the amount of blood returning to the heart and the ability of the heart to pump the blood into the arterial system. RAP is often nearly identical to central venous pressure (CVP), although the two terms are not identical, as a pressure differential can sometimes exist between the venae cavae and the right atrium. CVP and RAP can differ when venous tone (i.e the degree of venous constriction) is altered. This
168710
Post-thrombotic syndrome


to physical and psychological symptoms and limitations in daily activities. Despite ongoing research, the cause of PTS is not entirely clear. Inflammation is thought to play a role as well as damage to the venous valves from the thrombus itself. This valvular incompetence combined with persistent venous obstruction from thrombus increases the pressure in veins and capillaries. Venous hypertension induces a rupture of small superficial veins, subcutaneous hemorrhage and an increase of tissue permeability. That is manifested by pain, swelling, discoloration, and even ulceration. The following factors increase the
3613727
Fat embolism syndrome


(ARDS) when compared to those undergoing fixation after 24 hours (39% with ARDS). However, movement of the fracture ends of the long bones during the operative fixation can cause transient increase of fat emboli in the blood circulation. Cytokines are persistently elevated if the long bone fractures is treated conservatively using immobilisation. The cytokine levels would return to normal after operative fixation. Although ream nailing increases pressure in the medullary cavity of the long bones, it does not increase the rates of FES. Other methods such as drilling
4702045
Certificate of deposit


withdrawal must be the same as the real rate of return, in this case, zero. People may also think that the higher-rate situation is "better", when the real rate of return is actually the same. Also, the above does not include taxes. When taxes are considered, the higher-rate situation above is worse, with a lower (more negative) real return, although the before-tax real rates of return are identical. The after-inflation, after-tax return is what
4908585
Angiotensin


ACE), primarily through ACE within the lung (but also present in endothelial cells, kidney epithelial cells, and the brain). Angiotensin II acts on the CNS to increase vasopressin production, and also acts on venous and arterial smooth muscle to cause vasoconstriction. Angiotensin II also increases aldosterone secretion, therefore, it acts as an endocrine, autocrine/paracrine, and intracrine hormone. ACE is a target of ACE inhibitor drugs, which decrease the rate of angiotensin II production. Angiotensin II increases blood pressure by stimulating the Gq
25035
Compression stockings


causes more blood to return to the heart and less blood to pool in the feet. There are two types of compression stockings, gradient and anti-embolism. Treatment is usually prescribed by a physician to relieve all manifestations of chronic venous disease and prevent venous troubles. Compression stockings are recommended under the following conditions: Edema is a condition where the opposing forces that occur in the small blood vessels and capillaries cause a net ultrafiltration of plasma water into the soft tissues. Chronic peripheral venous insufficiency is when the veins cannot pump
6830369
Non-invasive measurement of intracranial pressure


cerebrospinal fluid whose pressure is equal to intracranial pressure. Intracranial hypertension will thus manifest in an increased diameter of the optic nerve sheath and will impede the blood flow through the central retinal vein that courses within the sheath, along and in part inside of the optical nerve. The impediment of venous return causes visible changes in the eye fundus (venous engorgement, and papilledema, i.e. swelling and elevation of the optic nerve disc) that can be observed with an ophthalmoscope and have therefore been used by clinicians for more than a century as
3570737
Orthostatic syncope


the patients' medication list may show polypharmacy, culprit medications (including diuretics, vasodilators, other antihypertensives) and steroids (a clue to steroid-induced adrenal insufficiency). Review of the past medical history will reveal associated predisposing medical conditions (diabetes, Parkinsonism, dementia). Patient compliance with both pharmacological and nonpharmacological therapy is recommended for successful treatment. Treatment of orthostatic syncope depends on the underlying cause and includes both nonpharmacological and pharmacological measures. Nonpharmacological treatment measures aim at either increasing venous return to the heart while decreasing venous pooling
719414
Venous ulcer


Venous ulcers are wounds that are thought to occur due to improper functioning of venous valves, usually of the legs (hence leg ulcers). They are the major occurrence of chronic wounds, occurring in 70% to 90% of leg ulcer cases. Venous ulcers develop mostly along the medial distal leg, and can be painful with negative effects on quality of life. Exercise together with compression stocking increases healing. The NICE guidelines recommends that everyone with a venous leg ulcer, even if healed, should be referred to a "
782303