Ventilator-induced subpleural air cysts: clinical, radiographic, and pathologic significance.

Alveolar rupture from the high airway pressures used in the treatment of adult respiratory distress syndrome may cause interstitial dissection of gas peripherally and the formation of "subpleural air cysts." These thin-walled, rounded air collections are easily detectable radiographically, and their recognition can provide an important early sign of pulmonary barotrauma. This report summarizes the clinical, radiographic, and pathologic features of this lesion in 5 adult patients. We found that tension pneumothorax rapidly occurs after the appearance of these cysts if airway pressures are not reduced or chest tubes are not in place. Secondary infection of the cysts was also common and added significant morbidity to this already compromised group of patients.