Life support refers to the treatments and techniques performed in an emergency in order to support life after the failure of one or more vital organs. Healthcare providers and emergency medical technicians are generally certified to perform basic and advanced life support procedures; however, basic life support is sometimes provided at the scene of an emergency by family members or bystanders before emergency services arrive. In the case of cardiac injuries, cardiopulmonary resuscitation is initiated by bystanders or family members 25% of the time. Basic life support techniques, such as performing CPR on a victim of cardiac arrest, can double or even triple that patient's chance of survival. Other types of basic life support include relief from choking (which can be done by using the Heimlich maneuver), staunching of bleeding by direct compression and elevation above the heart (and if necessary, pressure on arterial pressure points and the use of a manufactured or improvised tourniquet), first aid, and the use of an automated external defibrillator.