Subcutaneous and mediastinal emphysema. Pathophysiology, diagnosis, and management

• Subcutaneous emphysema and pneumomediastinum occur frequently in critically ill patients in association with blunt or penetrating trauma, soft-tissue infections, or any condition that creates a gradient between intra-alveolar and perivascular interstitial pressures. A continuum of fascial planes connects cervical soft tissues with the mediastinum and retroperitoneum, permitting aberrant air arising in any one of these areas to spread elsewhere. Diagnosis is made in the appropriate clinical setting by careful physical examination and inspection of the chest roentgenogram. While the presence of air in subcutaneous or mediastinal tissue is not dangerous in itself, prompt recognition of the underlying cause is essential. Certain trauma-related causes may require surgical intervention, but the routine use of chest tubes, tracheostomy, or mediastinal drains is not recommended. (<i>Arch Intern Med</i>1984;144:1447-1453)