| Mechanical ventilation |
In medicine, mechanical ventilation method to assist or replace spontaneous breathing. Mechanical ventilation can be life-saving and is a mainstay of CPR, intensive care medicine, and anesthesia.
Clinical use
Mechanical ventilation is used when natural (spontaneous) breathing is absent (apnea) or insufficient. This may be the case in cases of intoxication, circulatory arrest, neurological disease or head trauma, paralysis of the breathing muscles due to spinal cord injury, or the effect of anesthetic or muscle relaxant drugs. Various pulmonary diseases or chest trauma, cardiac disease such as congestive heart failure, sepsis and shock may also necessitate ventilation.
Depending on the situation, mechanical ventilation may be continued for a few minutes or many years. While returning to spontaneous breathing is rarely a problem in routine anesthesia, weaning an intensive care patient from prolonged mechanical ventilation can take weeks or even months. Some patients never adequately regain the ability to breathe and require permanent mechanical ventilation. This is often the case with severe brain injury, spinal cord injury, or neurological disease.
History
The iron lung was used through much of the middle 20th century, mostly for long-term ventilation. It was refined and used largely as a result of the polio epidemic that struck the world in the 1950s.
The machine is effectively a big 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.
By means of a pump, the air is withdrawn mechanically to provide inspiration and released to room pressure to allow expiration.
Thus the patient inhales room air by a means of negative pressure applied to the patient's thoracic area. There are large portholes for nurse or home assistant access. patients could remain in these iron lungs for years at a time quite successfully. Some are still in use, notably with the Polio Wing Hospitals in England such as St Thomas' (by Westminster in London) and the John Radcliffe in Oxford.
The patients can talk and eat normally and see the world through a well-placed series of mirrors.
A smaller device known as the cuirass was invented to place onto the chest wall like a giant plumber's suction plunger. It was prone to falling off and caused severe chaffing and skin damage and was not used as a long term device.
In recent years this device has re-surfaced as a modern polycarbonate shell with multiple seals and a high pressure oscillation pump. It has mostly been effective with children and is still in use in domiciliary ventilation in West England and Wales.
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