What are the common signs of a pneumothorax on physical examination?

A pneumothorax occurs when air enters the pleural space, leading to a collapse of the affected lung. On physical examination, the classic signs of a pneumothorax include decreased breath sounds and hyper-resonance upon percussion.

Decreased breath sounds are noted because the presence of air in the pleural space obstructs the normal transmission of sound from the lung to the chest wall. This results in a noticeable reduction in breath sounds when auscultating over the affected area.

Hyper-resonance on percussion occurs because the air in the pleural space creates an abnormal resonance compared to the normal, dull sound produced by the fluid in the chest cavity or the solid structures of the lung. When tapping over the area with a pneumothorax, the sound produced is more resonant, indicating the presence of air, which is a critical finding during the physical examination.

The other signs mentioned, such as bradycardia, hypotension, fever, or wheezing, do not specifically indicate a pneumothorax and are generally associated with different clinical conditions or complications. This makes decreased breath sounds and hyper-resonance the hallmark signs of a pneumothorax during a physical examination.