Physiologic factors in the use of the body respirator for impaired respiratory function.

It is of interest that the history of body-enclosing chambers for the treatment of respiratory diseases goes back to at least 1885, when H. F. Williams, an American physician, aided by an engineer friend, used this principle in administering aerosol therapy to patients with pulmonary infections.’ A year later Williams reported that cyclic changes in pressure around the body could be used to produce passive respiration and to assist breathing in diseased conditions.2 This experience was forgotten except in a few physiology laboratories where body plethysmographs were used to study respiration and produce ventilation in experimental animals.3 The idea was rediscovered in 1927 by Drinker and Shaw, and following their successful application of a respirator in treating poliomyelitis patients4 its use has spread to the treatment of other types of respiratory failure. Before considering physiologic aspects of the respirator, It is pertinent to review certain characteristics of the normal mechanics of breathing, gas exchange, and pulmonary circulation, since all of these components of external respiration are inseparably related to the interchange of carbon dioxide and oxygen between the body and the atmosphere. Likewise, all three components of external respiration are involved to various degrees in pulmonary diseases and are affected adversely or beneficially by the methods of therapy. Since the object of this report is consideration of the use of the respirator, most attention will be directed to the mechanics of breathing, but it must be kept in mind that mechanical ventilation of the lungs has little purpose except the regulation of alveolar gas concentrations, and the pressure changes in the thorax associated with ventilation, whether due to muscular activity or to a mechanical device, have inevitable effects on the circulation of blood through the thorax. Lung ventilation in the normal organism is so regulated that the alveolar partial pressure of carbon dioxide seldom varies