Modes<unk>  utilizes several separate systems for<unk>  referred to as the mode. Modes come in many different delivery concepts but all modes fall into one of three categories; volume-cycled, pressure-cycled, spontaneously cycled. In general, the selection of which mode of<unk>  to use for a given patient is based on the familiarity of clinicians with modes and the equipment availability at a particular institution. Positive pressure Carl Gunnar Engström invented in 1950 one of the first intermittent positive pressure ventilator, which delivers air straight into the lungs using an endotracheal tube placed into the windpipe. Neonatal<unk>  ventilator The design of the modern positive-pressure ventilators were based mainly on technical developments by the military during World War II to supply oxygen to fighter pilots in high altitude. Such ventilators replaced the iron lungs as safe endotracheal tubes with high-volume/low-pressure cuffs were developed. The popularity of positive-pressure ventilators rose during the polio epidemic in the 1950s in Scandinavia and the United States and was the beginning of modern<unk>  therapy. Positive pressure through manual supply of 50% oxygen through a tracheostomy tube led to a reduced mortality rate among patients with polio and respiratory paralysis. However, because of the sheer amount of man-power required for such manual intervention,<unk>  positive-pressure ventilators became increasingly popular. Positive-pressure ventilators work by increasing the patient's airway pressure through an endotracheal or tracheostomy tube. The positive pressure allows air to flow into the airway until the ventilator breath is terminated. Then, the airway pressure drops to zero, and the elastic recoil of the chest wall and lungs push the tidal volume — the breath-out through passive exhalation. Negative pressure machines Negative pressure<unk>  ventilators are produced in small, field-type and larger formats. The prominent design of the smaller devices is known as the cuirass, a shell-like unit used to create negative pressure only to the chest using a combination of a fitting shell and a soft bladder. In recent years this device has been manufactured using various-sized polycarbonate shells with multiple seals, and a high-pressure oscillation pump in order to carry out biphasic cuirass<unk> . Its main use has been in patients with neuromuscular disorders that have some residual muscular function. The latter, larger formats are in use, notably with the polio wing hospitals in England such as St Thomas' Hospital in London and the John Radcliffe in Oxford. The larger units have their origin in the iron lung, also known as the Drinker and Shaw tank, which was developed in 1929 and was one of the first negative-pressure machines used for long-term<unk> . It was refined and used in the 20th century largely as a result of the polio epidemic that struck the world in the 1940s. The machine is, in effect, a large elongated tank, which encases the patient up to the neck. The neck is sealed with a rubber gasket so that the patient's face (and airway) are exposed to the room air. While the exchange of oxygen and carbon dioxide between the bloodstream and the pulmonary airspace works by diffusion and requires no external work, air must be moved into and out of the lungs to make it available to the gas exchange process. In spontaneous breathing, a negative pressure is created in the pleural cavity by the muscles of respiration, and the resulting gradient between the atmospheric pressure and the pressure inside the thorax generates a flow of air. In the iron lung by means of a pump, the air is withdrawn<unk> ly to produce a vacuum inside the tank, thus creating negative pressure. This negative pressure leads to expansion of the chest, which causes a decrease in intrapulmonary pressure, and increases flow of ambient air into the lungs. As the vacuum is released, the pressure inside the tank equalizes to that of the ambient pressure, and the elastic recoil of the chest and lungs leads to passive exhalation. However, when the vacuum is created, the abdomen also expands along with the lung, cutting off venous flow back to the heart, leading to pooling of venous blood in the lower extremities. The patients can talk and eat normally, and can see the world through a well-placed series of mirrors. Some could remain in these iron lungs for years at a time quite successfully. Intermittent abdominal pressure ventilator Another type is the intermittent abdominal pressure ventilator that applies pressure externally via an inflated bladder, forcing exhalation, sometimes termed exsufflation. The first such apparatus was the Bragg-Paul Pulsator. The name of one such device, the Pneumobelt made by Puritan Bennett has to a degree become a generic name for the type. Monitoring In ventilated patients, pulse oximetry it is commonly used when titrating FIO2. A reliable target of Spo2 is greater than 95%. Different strategies exist to find the level of PEEP in these patients with ARDS guided by esophageal pressure, Stress Index, static airway pressure-volume curve. In such patients, some experts recommend limiting PEEP to low levels (~10cmH2O). In patients who have diffused loss of aeration, PEEP can be used provided it does not cause the plateau pressure to rise above the upper inflection point. Most modern ventilators have basic monitoring tools. There are also monitors that work independently of the ventilator which allow for measuring patients after the ventilator has been removed, such as a T tube test. Withdrawal from<unk>  Timing of withdrawal from<unk> —also known as weaning—is an important consideration. People who require<unk>  should have their<unk>  considered for withdrawal if they are able to support their own<unk>  and oxygenation, and this should be assessed continuously. There are several objective parameters to look for when considering withdrawal, but there are no specific criteria that generalizes to all patients. The Rapid Shallow Breathing Index (RSBI, the ratio of respiratory frequency to tidal volume (f/VT), previously referred to as the "Yang Tobin Index" or "Tobin Index" after Dr. Karl Yang and Prof. Martin J. Tobin of Loyola University Medical Center) is one of the best studied and most commonly used weaning predictors, with no other predictor having been shown to be superior. It was described in a prospective cohort study of<unk> ly ventilated patients which found that a RSBI > 105 breaths/min/L was associated with weaning failure, while a RSBI < 105 breaths/min/L predicted weaning success with a sensitivity, specificity, positive predictive value and negative predictive value of 97%, 64%, 78%, 95% respectively. Types of ventilators SMART BAG MO Bag-Valve-Mask Resuscitator Ventilators come in many different styles and method of giving a breath to sustain life. There are manual ventilators such as bag valve masks and anesthesia bags that require the users to hold the ventilator to the face or to an artificial airway and maintain breaths with their hands.<unk>  ventilators are ventilators not requiring operator effort and are typically computer-controlled or pneumatic-controlled.<unk>  ventilators typically require power by a battery or a wall outlet (DC or AC) though some ventilators work on a pneumatic system not requiring power. There are a variety of technologies available for<unk> , falling into two main (and then lesser categories), the two being the older technology of negative-pressure mechanisms, and the more common positive-pressure types. Common positive-pressure<unk>  ventilators include: #Transport ventilators—These ventilators are small and more rugged, and can be powered pneumatically or via AC or DC power sources. #Intensive-care ventilators—These ventilators are larger and usually run on AC power (though virtually all contain a battery to facilitate intra-facility transport and as a back-up in the event of a power failure). This style of ventilator often provides greater control of a wide variety of<unk>  parameters (such as inspiratory rise time). Many ICU ventilators also incorporate graphics to provide visual feedback of each breath. #Neonatal ventilators (bubble CPAP)—Designed with the preterm neonate in mind, these are a specialized subset of ICU ventilators that are designed to deliver the smaller, more precise volumes and pressures required to ventilate these patients. #Positive airway pressure ventilators (PAP) — These ventilators are specifically designed for non-invasive<unk> . This includes ventilators for use at home for treatment of chronic conditions such as sleep apnea or COPD. Breath delivery mechanisms Trigger The trigger is what causes a breath to be delivered by a<unk>  ventilator. Breaths may be triggered by a patient taking their own breath, a ventilator operator pressing a manual breath button, or by the ventilator based on the set breath rate and mode of<unk> . Cycle The cycle is what causes the breath to transition from the inspiratory phase to the exhalation phase. Breaths may be cycled by a<unk>  ventilator when a set time has been reached, or when a preset flow or percentage of the maximum flow delivered during a breath is reached depending on the breath type and the settings. Breaths can also be cycled when an alarm condition such as a high pressure limit has been reached, which is a primary strategy in pressure regulated volume control. Limit Limit is how the breath is
Mechanical ventilation
Negative pressure ventilator
Artificial ventilation
Positive airway pressure
Non-invasive ventilation
High-frequency ventilation
Pressure support ventilation
Surfactant therapy