Postoperative pulmonary complications occur in from 2 to 4 per cent of all operative interventions. When operations on the upper abdominal region alone are considered, this figure rises to 10 per cent and higher. The mortality from the same cause is given as 0.6, or one in every 200 cases. The view that ether anesthesia, because of its chilling effect on the lung and the increased possibility for aspiration of septic contents from the mouth into the bronchial tree, was largely responsible, was abandoned when studies revealed that the introduction of local and spinal anesthesia did not diminish either the morbidity or the mortality from this cause.
Research on the pathogenesis of the postoperative pulmonary complications resulted in three distinct theories: that of aspiration pneumonitis developed by A. O. Whipple; that of infected emboli supported by Lichtenberg, Wölfler, Cutler and Morton, Cutler and Hunt, and others; and, more recently, that