Basic life support is the maintenance of an airway and the support of breathing and the circulation without using equipment other than a simple airway device or protective shield. A combination of expired air ventilation (rescue breathing) and chest compression is known as cardiopulmonary resuscitation (CPR), which forms the basis of modern basic life support. The term “cardiac arrest” implies a sudden interruption of cardiac output, which may be reversible with appropriate treatment. It does not include the cessation of heart activity as a terminal event in serious illness; in these circumstances the techniques of basic life support are usually inappropriate.