Pneumothorax, Tension and Traumatic

Background

A pneumothorax refers to a collection of gas in the pleural space resulting in collapse of the lung on the affected side. A tension pneumothorax is a life-threatening condition caused by air within the pleural space that is under pressure; displacing mediastinal structures and compromising cardiopulmonary function. A traumatic pneumothorax results from blunt or penetrating injury that disrupts the parietal or visceral pleura. Mechanisms include injuries secondary to medical or surgical procedures.

Pathophysiology

A tension pneumothorax results from any lung parenchymal or bronchial injury that acts as a one-way valve and allows free air to move into an intact pleural space but prevents the free exit of that air. In addition to this mechanism, the positive pressure used with mechanical ventilation therapy can cause air trapping.

As pressure within the intrapleural space increases, the heart and mediastinal structures are pushed to the contralateral side. The mediastinum impinges on and compresses the contralateral lung.

Hypoxia results as the collapsed lung on the affected side and the compressed lung on the contralateral side compromise effective gas exchange. This hypoxia and decreased venous return caused by compression of the relatively thin walls of the atria impair cardiac function. The decrease in cardiac output results in hypotension and, ultimately, in hemodynamic collapse and death to the patient, if untreated.