Life support refers either to medical intervention used to sustain an individual’s life or to specialized equipment that provides appropriate environmental conditions to sustain many lives, such as in a submarine, airplane, or space craft. In a medical situation, life support involves any number of medical techniques and paraphernalia used to keep a person alive if he is unable to survive on his own. Some examples of life support include cardiopulmonary resuscitation (CPR), feeding tubes, intravenous fluids, mechanical respiration, heart and lung bypass instruments, defibrillation equipment, and renal dialysis. In most cases, a person who requires life support is unconscious.

A person in need of life support may have suffered a serious traumatic injury, such as a car accident, a debilitating stroke or heart attack, or any number of vital organ failures. Some people feel very strongly against the use of life support and issue a do not resuscitate (DNR) order. Sometimes, life support is only necessary for a temporary period of time, but in some cases, such as when a person is in a coma, life support may be used for years. These cases are often heart wrenching for families and a source of disagreement as to whether or not the person should remain on life support indefinitely. Many people refer to the decision to discontinue life support as pulling the plug.

The National Aeronautics and Space Administration (NASA) has developed a life support system, called the environmental control and life support system (ECLSS), that is used in space stations. This system is made up of highly specialized equipment that works to provide oxygen, water, and stable air pressure and temperature. This equipment also removes carbon dioxide and volatile gases from the air and filters out particulates and microorganisms. Life support systems that are used on earth as a control for environmental conditions are found on commercial airplanes, submarines, and other vehicles where hostile conditions cannot sustain human life.