Which vital sign would raise suspicion for a pneumothorax?

The sudden onset of unilateral chest pain coupled with decreased breath sounds is highly indicative of a pneumothorax. A pneumothorax occurs when air enters the pleural space, leading to a collapse of the lung on the affected side. The acute nature of the pain is a common symptom and is often sharp and localized. The presence of decreased or absent breath sounds on the affected side is a critical finding, as it suggests that the lung may not be fully expanding due to the intrusion of air in the pleural cavity.

In contrast, while gradual chest pain is often associated with other pulmonary or cardiac conditions, it does not typically signify a pneumothorax, which presents more acutely. An increased respiratory rate may occur with many different conditions, including anxiety or other types of respiratory distress, but it is not specific to pneumothorax. A low heart rate generally does not correlate with pneumothorax and might suggest other issues, such as increased vagal tone or other cardiovascular concerns. Thus, the combination of sudden chest pain and decreased breath sounds is the most telling sign of a pneumothorax.