The physiology of artificial ventilation

Abstract

In 1543 Vesalius demonstrated that a pig could be kept alive by tracheal intubation and rhythmical inflation of the lungs under positive pressure. A century later Robert Hooke repeated the experiment in a dog and in 1825 Charles Waterton’ used bellows ventilation to sustain life in an ass paralysed with curare. Development of artificial ventilation in man lagged behind these animal experiments but in the late 18th century the Royal Humane Society advocated the use of bellows to resuscitate those apparently drowned. The success rate was poor, in part due to pneumothoraces produced by overenthusiastic inflation. Two Americans, O’Dwyer and Fell, reintroduced positive pressure ventilation (PPV) a hundred years later and in 1912 the Prussian surgeon, Lawen, used it to reduce the amount of ether required for abdominal surgery. In the 1890s the particular demands of thoracic anaesthesia induced a greater use of PPV but its more general acceptance awaited the introduction of the muscle relaxants 20 years later. Despite all the evidence to the contrary there remained a widespread belief that prolonged PPV would lead to disastrous and irreversible physiological changes. Consequently much complex apparatus was developed that attempted to mimic normal respiratory mechanics by creating a negative pressure outside the chest wall. Some of this apparatus was elegant, much was cumbersome and on the whole it was ineffective and impractical to use on sick patients. In 1904 Sauerbruch had the patient’s head (and the anaesthetist) outside the operating theatre, but the body (together with the surgeon and assist-