Hypoxia, the result of insufficient oxygen in the blood, is a potentially deadly condition and one of the leading causes of cardiac arrest. Cardiac arrest is the ultimate cause of clinical death for all animals (although with advanced intervention, such as cardiopulmonary bypass a cardiac arrest may not necessarily lead to death), and it is linked to an absence of circulation in the body, for any one of a number of reasons. For this reason, maintaining circulation is vital to moving oxygen to the tissues and carbon dioxide out of the body.