In an emergency, when should CPR be performed?

CPR, or cardiopulmonary resuscitation, should be performed when a casualty is unresponsive and not breathing. This situation indicates that the individual's heart may have stopped beating or they are experiencing a severe respiratory issue, leading to a life-threatening emergency. In such cases, immediate action is crucial as CPR helps maintain blood flow to the vital organs, particularly the brain, until professional medical assistance can be provided.

The correct answer emphasizes the importance of recognizing unresponsiveness and the absence of normal breathing as critical indicators for the need for CPR. By acting promptly under these circumstances, a bystander can significantly improve the casualty's chances of survival and recovery.