What is a common sign of a pneumothorax?

A common sign of a pneumothorax is that the trachea deviates towards the unaffected side. This occurs because the air that accumulates in the pleural space during a pneumothorax leads to increased pressure on the affected lung, causing it to collapse. The mediastinum, including the trachea, may shift towards the side that is not affected by the pneumothorax due to this pressure difference.

In addition to tracheal deviation, other clinical signs may include decreased breath sounds on the affected side, dyspnea, and tachycardia. However, the key feature indicating a tension pneumothorax specifically is the tracheal shift towards the unaffected side, as this indicates significant pressure buildup in the pleural space.

The other options may not directly reflect typical presentations associated with a pneumothorax, making them less indicative of this condition compared to tracheal deviation.