A pneumothorax occurs when air enters the pleural cavity through a lung or chest wall injury; a tension pneumothorax is a distinct, life-threatening subtype caused by a one-way valve effect that admits air during inspiration but traps it during expiration, so pressure accumulates progressively with each breath. This rising intrapleural pressure compresses the ipsilateral and eventually contralateral lung (causing hypoxia), directly compresses the heart and reverses the normal negative intrathoracic pressure gradient (impairing cardiac filling and venous return), producing a form of obstructive shock in addition to respiratory compromise. This is emergency/trauma medicine physiology and diagnostic reasoning, distinguishing tension pneumothorax (a clinical diagnosis requiring immediate needle decompression as temporizing treatment before definitive chest-tube management) from simple pneumothorax (hemodynamically benign, without the one-way valve mechanism).
A pneumothorax occurs when air enters the pleural cavity through a lung or chest wall injury; a tension pneumothorax is a distinct, life-threatening subtype caused by a one-way valve effect that admi…