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Mechanical ventilators

A polio patient being placed in an iron lung, 1938.

A polio patient being placed in an iron lung, 1938.

Credits:Daily Herald Archive/NMeM/SSPL

If the body is without oxygen death usually occurs within minutes. Machines helping patients breathe are called mechanical ventilators.

The earliest breathing machine was the Drinker respirator. It was invented in 1928 and was known as an ‘iron lung’. These machines were used between the 1930s and 1950s by patients whose breathing muscles had been paralysed by polio. They used negative pressure to help patients breathe while lying inside the iron lung’s airtight chamber. A pump removed air inside the chamber, creating low air pressure around the patient’s chest. This enabled the lungs to expand, causing the patient to breathe in. Other negative-pressure devices included the cuirass, a shell-like device that was tightly strapped over the chest. A pump created a vacuum across the chest, forcing the patient to breathe in.

Ventilators replaced respirators during the 1950s. They use positive pressure, meaning they pump air into the lungs through a face mask or a tube in the throat. Ventilators were developed during the Second World War to supply oxygen to fighter pilots flying at high altitude. Hand-pumped and mechanical positive-pressure devices helped patients breathe during polio epidemics in the 1950s. Ventilators were less bulky than negative-pressure devices.

Ventilators became essential tools within surgery as well as in intensive-care medicine. In 1949, American engineer John Haven Emerson developed an anaesthetic ventilator. Regulating patient breathing made operations more straightforward.


Related links

External links:


G Lawrence, ‘The Smith-Clarke respirator’, Lancet, 359 (2002), p 716

A Barrington Baker, ‘Artificial respiration: the history of an idea’, Medical History, 15 (1971), pp 336-351

P Drinker and C McKhann, ‘The use of a new apparatus for the prolonged administration of artificial respiration. I: A fatal case of poliomyelitis’, Journal of the American Medical Association, 255 (1986),  pp 1473-1475

P Drinker and C McKhann, ‘The iron lung: first practical means of respiratory support’, Journal of the American Medical Association 255 (1986), pp 1476-1480

G L Colice, ’Historical Perspective on the Development of Mechanical Ventilation‘ in M J Tobin (ed.), Principles & Practice of Mechanical Ventilation (New York: McGraw-Hill, 2006



The loss of function in one or more muscle groups. It causes loss of mobility and feeling.


An infectious disease affecting the central nervous system. Affected individuals can exhibit a range of symptoms if the polio virus enters the blood stream.


A type of ventilator worn around the chest to aid breathing.


An agent that causes insensitivity to pain. Applied to either the whole body (general anaesthetic) or a particular area or region (local anaesthetic).