In recent years a great deal of attention has been paid to the subject of pulmonary collapse, or atelectasis. Atelectasis may occur as a secondary manifestation of some bronchopulmonary condition or as a postoperative complication. In the opinion of that eminent physician Frederick Lord:1 "The clinical recognition of atelectasis as a common and important complication of various bronchopulmonary conditions is the most important single advance in physical diagnosis since the time of Laennec."
Although the clinical and roentgen diagnosis of frank atelectasis is comparatively simple, there is still some controversy as to the etiology and pathogenesis of this condition. This paper will be limited to a consideration of postoperative pulmonary collapse.
It has been found that atelectasis occurs most frequently after abdominal operations, especially those on the upper part of the abdomen. In the series of laparotomies studied by Muller, Overholt and Pendergrass,2 postoperative measurements showed a marked reduction in