Which assessment finding is a hallmark symptom of tension pneumothorax?

The hallmark symptom of tension pneumothorax is characterized by decreased breath sounds on the affected side. In tension pneumothorax, air enters the pleural space and cannot escape, leading to increased intrathoracic pressure. This accumulation of pressure causes the lung on the affected side to collapse, which results in diminished or absent lung sounds during auscultation. The presence of severe respiratory distress and significant changes in lung mechanics contribute to this finding.

While decreased breath sounds are a key indicator for identifying the condition, the other options may also be present in cases of tension pneumothorax but are not as specific. Paradoxical chest movement can occur in various conditions, typically associated with flail chest. Hypotension and severe tachycardia can be associated with the hemodynamic instability that arises from tension pneumothorax but are more general symptoms of shock or respiratory distress rather than definitive signs. Thus, decreased breath sounds stand out as the more specific assessment finding in the context of tension pneumothorax.