Cardiopulmonary resuscitation (CPR) is an emergency first-aid procedure used to deliver oxygen-carrying blood to the heart and brain in a person whose breathing and heartbeat have stopped. CPR is most often needed following a heart attack that has caused a person's heart to stop beating, a condition called cardiac arrest. People may also go into cardiac arrest and require CPR after serious injury, after nearly drowning, or after a drug overdose. CPR must begin within minutes after the victim's breathing and heartbeat have stopped.