Cardiopulmonary resuscitation (CPR) is an emergency medical procedure for a victim of cardiac arrest or, in some circumstances, respiratory arrest. CPR is performed in hospitals, or in the community by laypersons or by emergency response professionals. CPR consists of artificial blood circulation and artificial respiration (i.e. chest compressions and lung ventilation). CPR is generally continued, usually in the presence of advanced life support, until the patient regains a heart beat (called "return of spontaneous circulation" or "ROSC") or is declared dead. CPR is unlikely to restart the heart, but rather its purpose is to maintain a flow of oxygenated blood to the brain and the heart, thereby delaying tissue death and extending the brief window of opportunity for a successful resuscitation without permanent brain damage. Defibrillation and advanced