"Emerson developed a respirator selling for less than $1000 and solved... breathing-rate changes."
Charles C. Smith, Jr., Special Air Mission: Polio
After working to improve the iron lung in 1931, American biomedical device inventor John Emerson (1906-1997) went on to develop a mechanical ventilator. A ventilator is a machine that automatically moves air into and out of the lungs of a patient who is unable to breathe. Emerson worked on his mechanical assistor with colleagues in the department of anesthesia at Harvard University in 1949. Polio epidemics of the 1940s had increased the demand for such machines, as had an increased use of muscle relaxant drugs during surgery; these would paralyze the patients' respiratory muscles so that they could not breathe. Other models followed Emerson's through the 1950s, such as the Bird ventilator, driven only by gas. In Britain the East Radcliffe and Beaver models were used; the Beaver ventilator had an automotive wiper motor that operated bellows to inflate the lungs. But such motors were dangerous in surgical environments where flammable anesthetics were used. The Manley ventilator of 1952 was another gas driven model and so got around this problem. The Manley Mark II became popular and was made and sold in the thousands. Manley's ventilators led to positive-pressure ventilation techniques being used widely across Europe.
In the 1980s high-frequency percussive ventilators, combining mechanical ventilation and high- frequency oscillatory ventilation, were introduced.
