Rupture of the lung from overexpansion sometimes occurs during artificial ventilation. In 1912, Woolsey1 described two patients who died when lung rupture occurred during insufflation anesthesia. Kirschner,2 reviewing the autopsy findings in 497 consecutive cases of infants born alive but dying shortly after birth, found lung rupture present in 47 cases. Hypotrophic lungs may have contributed to the findings in eight of these; the remainder were thought to be caused by spontaneous ventilatory efforts in the presence of absorption atelectasis, or to excessive inflation. Kinsey3 and Liebow, et al4 reported air cardiac tamponade and interstitial pulmonary emphysema with a bilateral tension pneumothorax as autopsy findings in cases of accidental death occurring during submarine escape training. While breathing compressed air, a skin diver ascending rapidly with a closed glottis maintains a high intratracheal pressure while reducing external chest compression. Excessive expansion and rupture of the lungs may