Cardiopulmonary resuscitation, or CPR, is an emergency procedure performed on people suffering cardiac arrest. The purpose of CPR is to provide a continuous flow of oxygen to the lungs and brain until the person regains consciousness. The human brain can only survive an average of five minutes without oxygen, after which time permanent damage is done. By performing CPR on a victim, the rescuer is upping the chances for a full recovery. However, it is important to remember that CPR alone is rarely enough for a person to survive. The true purpose of CPR is to keep the heart pumping and the oxygen flowing until emergency care arrives.

CPR is often used when no other assistance methods, such as defibrillators, are available, but it can also be done by medical professionals on patients who have just recently lost their pulse. The International Consensus Conference on CPR and Emergency Cardiovascular Care Science, which was held in 2005, established that it is not longer necessary for health professionals to check for a pulse before starting CPR. In fact, it is believed that many victims could have been saved if CPR had been performed on them earlier on; it is now at discretion of individuals as to when CPR should be started, which means health professionals will more than likely start the procedure much earlier than they did before.

CPR is performed by alternating chest compressions and mouth-to-mouth breathing. The standard is thirty chest compressions followed by two deep rescue breaths and back to chest compressions immediately. CPR is performed on people who have drowned, suffered a heart attack, or experienced a drug overdose or poisoning. CPR can also be performed in chocking victims when all else has failed.

CPR can be performed on children of any age, including babies, and in animals. On animals, CPR is performed by pressing down on the left side, on the upper part of the ribcage, and blowing air into the nose, not the mouth. On infants, the procedure is the same as in adults, although the pressure exerted in the chest should be much less.

Recently, the American Heart Association has issued a recommendation for bystanders to perform "Hands-Only CPR" on adults who suddenly collapse. While some situations such as drowning require traditional CPR, hands-only CPR has proven to be about as effective in situations that involve sudden cardiac arrest. Hands-only CPR consists of CPR without rescue breathing.