Pneumothorax (tension)

[Dorothey Allen]

Tension pneumothorax is accumulation of air in the pleural space under pressure, compressing the lungs and decreasing venous return to the heart.
(See also Overview of Thoracic Trauma.)
Tension pneumothorax develops when a lung or chest wall injury is such that it allows air into the pleural space but not out of it (a one-way valve). As a result, air accumulates and compresses the lung, eventually shifting the mediastinum, compressing the contralateral lung, and increasing intrathoracic pressure enough to decrease venous return to the heart, causing shock. These effects can develop rapidly, particularly in patients undergoing positive pressure ventilation.
Causes include mechanical ventilation (most commonly) and simple (uncomplicated) pneumothorax with lung injury that fails to seal following penetrating or blunt chest trauma or failed central venous cannulation.