Cardiopulmonary resuscitation: The emergency substitution of heart and lung action to restore life to someone who appears dead. The two main components of conventional cardiopulmonary resuscitation (CPR) are chest compression to make the heart pump and mouth-to-mouth ventilation to breath for the victim. Hands-only CPR is a form of resuscitation that involves continuous, rapid chest compressions only, and although effective, it is not as beneficial as conventional CPR in a patient who is not breathing.

In the event of an early heart attack, death can often be avoided if a bystander calls emergency services (911) and starts CPR promptly. Hands-only CPR was approved by the American Heart Association in April 2008 as a measure to allow untrained or fearful bystanders to be able to initiate help in the event of a cardiac arrest. If others are present, one person should attempt to locate an automated external defibrillator (AED) while another administers CPR.