Increasing awareness of the importance of pulmonary embolism is becoming apparent in the thinking of surgeons and internists alike. Many aspects of the problem have been studied in the laboratory and at the bedside; yet there is still much to be learned concerning both the prophylaxis and the management of this important and extremely common complication in medical, surgical and obstetric patients. The possibility that bronchospasm may be associated with pulmonary embolism, with material increase in respiratory distress and anoxemia, has been suggested by several investigators. In 1920 Dunn1 described histologic changes in embolized lungs consisting of spasm of the musculature of the bronchiolar terminations and of the atria, but not of the bronchioles themselves. In 1924, however, Binger, Brow and Branch2 observed similar changes in normal, nonembolized lungs. Singh,3 using an oncometer to measure changes in the lung volume of decapitated cats, reported that air embolism