What is the pathophysiology of tension pneumothorax?

Updated: Apr 28, 2020
  • Author: Brian J Daley, MD, MBA, FACS, FCCP, CNSC; Chief Editor: Mary C Mancini, MD, PhD, MMM  more...
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Answer

Tension pneumothorax occurs anytime a disruption involves the visceral pleura, parietal pleura, or the tracheobronchial tree. This condition develops when injured tissue forms a one-way valve, allowing air inflow with inhalation into the pleural space and prohibiting air outflow. The volume of this nonabsorbable intrapleural air increases with each inspiration because of the one-way valve effect. As a result, pressure rises within the affected hemithorax. In addition to this mechanism, the positive pressure used with mechanical ventilation therapy can cause air trapping.

As the pressure increases, the ipsilateral lung collapses and causes hypoxia. Further pressure increases cause the mediastinum to shift toward the contralateral side and impinge on and compress both the contralateral lung and impair the venous return to the right atrium. 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. Kinking of the inferior vena cava is thought to be the initial event restricting blood to the heart. It is most evident in trauma patients who are hypovolemic with reduced venous blood return to the heart.

Arising from numerous causes, this condition rapidly progresses to respiratory insufficiency, cardiovascular collapse, and, ultimately, death if unrecognized and untreated.


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