Pulmonary barotrauma

[Michiko]

Barotrauma is tissue injury caused by a pressure-related change in body compartment gas volume. Factors increasing risk of pulmonary barotrauma include certain behaviors (eg, rapid ascent, breath-holding, breathing compressed air) and lung disorders (eg, chronic obstructive pulmonary disease). Pneumothorax and pneumomediastinum are common manifestations. Patients require neurologic examination and chest imaging. Pneumothorax is treated. Prevention involves decreasing risky behaviors and counseling high-risk divers.
(See also Overview of Diving Injuries and Overview of Barotrauma.)
Overexpansion and alveolar rupture can occur when breath-holding occurs (usually while breathing compressed air) during ascent, particularly rapid ascent. The result can be pneumothorax (causing dyspnea, chest pain, and unilateral decrease in breath sounds) or pneumomediastinum (causing sensation of fullness in the chest, neck pain, pleuritic chest pain that may radiate to the shoulders, dyspnea, coughing, hoarseness, and dysphagia). Pneumomediastinum may cause crepitation in the neck, due to associated subcutaneous emphysema, and a crackling sound may rarely be heard over the heart during systole (Hamman sign). Air can sometimes track caudad into the peritoneal cavity (falsely suggesting a ruptured viscus and the need for laparotomy), but it does not typically cause peritoneal signs. Tension pneumothorax, although rare with barotrauma, can cause hypotension, distended neck veins, hyperresonance to percussion, and, as a late finding, tracheal deviation. Alveolar rupture can allow air into the pulmonary venous circulation with subsequent arterial gas embolism.
During very deep breath-hold diving, compression of the lungs during descent may rarely lead to a decrease in volume below residual volume, causing mucosal edema, vascular engorgement, and hemorrhage, which manifest clinically as dyspnea and hemoptysis on ascent.