Early technology: Patient receives a shave while in a negative pressure iron lung.

“Negative pressure ventilation first came into use during the second half of the nineteenth century. It was recognized that air would be drawn into the lungs through the mouth and nose if a sub-atmospheric pressure could be developed around the thorax and abdomen. When the pressure around the chest wall returned to that of the ambient air, expiration occurred passively owing to the elastic recoil of the lungs and chest wall.”

Non-invasive and domiciliary ventilation: negative pressure techniques

by John M Shneerson