[Subpleural air cysts. A complication of barotrauma during mechanical ventilation].

The presence of air in the interstitial pulmonary tissues is shown as interstitial emphysema and is often the first sign of barotrauma. It results from hyper-pressure in the airways occurring for the greater part of the time on some underlying pulmonary pathology. This extra alveolar air may diffuse into the interstitium and collect under the visceral pleura, appearing on radiographs as air cysts from 3 to 10 centimeters in diameter. We described 7 cases of air cysts occurring in adults on mechanical ventilation. The lesions seem to us to represent a radiological entity and evidence of barotrauma due to mechanical ventilation and possessing its own potential outcome, namely rupture leading to pneumothorax, infection, persistence, or disappearance. The early occurrence in its history of a particular disease should be noted, enabling one to minimise the factors contributing to the barotrauma.