The role of negative pressure ventilation.

In the 3rd century BC Erasistratus of Chios recognised that breathing depended on muscular action. By 1555 Vesalius had described assisted positive pressure ventilation and in 1667 Hooke used a pair of bellows to keep a dog alive in his demonstration to the Royal Society. By the mid-1800s it was recognised that air would be drawn into the lungs through the mouth and nose if a subatmospheric pressure could be developed around the thorax and abdomen, and the first body enclosing negative pressure ventilators developed. These experimental devices were gradually refined and the first negative pressure ventilator to be of clinical value was described by Drinker in 1928. This tank ventilator or ‘iron lung’ in its many modifications was widely used in the polio epidemics from 1930 to 1960 and saved many lives. The iron lung has many disadvantages. It is bulky, cumbersome, and limits access to the patients. Simpler non-tank negative pressure ventilators were developed in the 1950s and 1960s, with cuirasses, negative pressure jackets, or wraps, all of which fitted over the trunk and abdomen. In all of these designs inspiration was controlled, but expiration relied on passive recoil of the lung and so this was a rather ineYcient form of ventilation. By the 1950s the greater eYciency of positive pressure ventilation delivered through a tracheostomy or endotracheal tube had been demonstrated and negative pressure ventilation fell out of favour, with its use largely restricted to chronic ventilatory support in neuromuscular disorders. Over the past 10 years, however, the development of newer forms of negative pressure ventilators which overcome in large measure the drawbacks of their predecessors has seen a resurgence of interest in this mode of ventilation for children.