Subcutaneous emphysema is a result of leakage of air under sufficient pressure to track into the subcutaneous tissues. As with any gas or fluid, air under pressure will seek the exit path of least resistance. If a chest drain is occluded either by kinking, clamping, or clogging of the tubing with fibrinous material or clot, continued air leak from the pulmonary parenchyma will seek a different path of exit from the pleural space. This also can occur if a volume of “stagnant” fluid remains in a dependent loop of the connecting tubing, as described previously. The increased intrapleural pressure will promote lung collapse and subsequent tracking of air through breaches in the parietal pleura into the subcutaneous tissues.
If subcutaneous emphysema develops, a thorough evaluation of the tubing and collection system is indicated. A chest radiograph is important to assess the lung. Any obstruction within the tubing must be cleared to favor egress of air through the drain over any other pathway. An initial maneuver to consider is to restart suction on the drain by means of the underwater seal device. If the tubing is patent, restarting suction may be all that is needed. Evaluation of the pleural space with computed tomography (CT) may help identify the area requiring further drainage. The parenchymal air leak may be of such magnitude that a second chest tube is required. On rare occasions, surgical repair of the air leak may be necessary.
Subcutaneous emphysema can be quite disfiguring and thus extremely distressing to affected patients and their families. Appropriate management should therefore include reassurance that although dramatic in appearance, this is rarely a dangerous situation, that the condition usually will require more time to resolve than it took to appear, but that it will ultimately resolve.