What is the hallmark sign of a tension pneumothorax?

The hallmark sign of a tension pneumothorax is tracheal deviation away from the affected side. In a tension pneumothorax, air enters the pleural space and cannot escape, leading to increased intrathoracic pressure. This pressure builds to the point where it affects mediastinal structures, including the trachea, which shifts away from the side where the pneumothorax has occurred.

As the trachea deviates, other critical structures, including major blood vessels and the heart, can also be displaced, which results in compromised cardiovascular function and causes symptoms such as hypotension and decreased breath sounds on the affected side. While chest pain and hypotension are common symptoms of tension pneumothorax, they are not as definitive as the tracheal deviation in diagnosing this acute condition.