Which of the following is a potential sign of tension pneumothorax?

A potential sign of tension pneumothorax is characterized primarily by the development of progressive respiratory distress in the casualty. This occurs because air enters the pleural space but cannot escape, leading to increased pressure that compresses the lungs and restricts breathing.

Additionally, a casualty's pulse may become difficult to detect at the wrist due to decreased venous return to the heart caused by mediastinal shift from increasing intrathoracic pressure. As pressure builds in the pleural cavity, it can compress major blood vessels, affecting the heart's ability to pump effectively and diminishing peripheral circulation. Both of these symptoms—progressive respiratory distress and changes in pulse—are indicative of compromised respiratory and cardiovascular function associated with tension pneumothorax.

Therefore, recognizing both signs is critical for timely diagnosis and intervention, making the option that includes both signs the correct choice.