Cardiopulmonary resuscitation (CPR) is an emergency first aid protocol for a victim of cardiac arrest. It can be performed by trained lay persons or by healthcare or emergency response professionals. It is normally begun on an unbreathing unconscious person and continued until action can be taken to restart the heart or otherwise diagnose the problem. CPR essentially consists of a pattern of chest compressions and rescue breaths (i.e. artificial blood circulation and lung ventilation) and is intended to maintain a trickle of oxygenated blood to the brain and the heart and thereby extend the otherwise brief window of opportunity for successfully restarting the heart without permanent brain damage. CPR itself is not intended to restart the heart but must be performed continuously until medical responders can attempt to restart the heart by other means.