Skip to main content
Select Source:

Life Support

Life Support

Definition

Life support refers to a spectrum of techniques used to maintain life after the failure of one or more vital organs.

Purpose

A patient requires life support when one or more vital organs fail, due to causes such as trauma, infection, cancer, heart attack, or chronic disease. Among the purposes of life support are to:

  • Establish and maintain the ABC's of resuscitationairway, breathing, and circulation.
  • Restore the patient's homeostasisthe internal chemical and physical balance of the body.
  • Protect the patient from complications of the underlying disease and its treatment.

Precautions

Patients and families need to recognize that life support is an extremely painful, expensive, and emotionally wrenching experience. Life support exposes a patient to vast risks of further medical complications, and offers no guarantee of a positive outcome. Even in successful cases, recovery may be slow and frustrating.

Description

Successful life support begins with establishing the ABC's of resuscitationairway, breathing, and circulation.

The airway refers to a clear passageway for air to enter the lungs from outside the body. The patient's airway may become blocked by:

  • Foreign body obstruction, as by food or dentures
  • Injury-related damage and swelling, as from a wound or surgery
  • Loss of protective reflexes due to coma of any origin

Life support may begin with basic cardiopulmonary resuscitation (CPR), as in cases of cardiac arrest. Thereafter, the most common technique used to create a secure airway is insertion of an endotracheal (ET) tube through the mouth or nose into the windpipe (trachea). An alternative method of securing an airway is by tracheotomy, a surgical procedure in which a tube is inserted into the trachea through an incision made in the base of the throat. Of the two options, placement of an ET tube is usually quicker and more convenient, and thus occurs much more commonly. Doctors perform a tracheotomy when they cannot establish an ET airway, or when the patient will require an artificial airway for more than a week or two.

Breathing refers to the movement of air in and out of the lungs. Inadequate breathing may result from:

  • Heart disease, as in congestive heart failure
  • Primary disease of the lungs, such as pneumonia, asthma, or emphysema
  • Coma of any cause, such as narcotic overdose or stroke
  • Muscle fatigue or neuromuscular disease (spinal cord injury or polio)
  • Pain, from rib fractures or surgery on the chest

When the patient cannot breathe sufficiently, the physician will use a ventilator, a machine that pumps air in and out of the patient's lungs. For many doctors and members of the public, the term "life support" calls up the image of an ET tube and ventilator.

Circulation refers to the flow of blood around the body from the heart to vital organs. Circulation can fail due to:

  • Primary disease of the heart (heart attack)
  • Blood loss (trauma or internal bleeding of any cause)
  • Severe infection (sepsis)
  • Drug reactions or overdoses
  • Extreme allergic reaction
  • Severe dehydration (gastroenteritis or heat-related illness)

In order to ensure adequate circulation, the patient will require one or more intravenous (IV) tubes (catheters). The IVs may include both the short needle and tube commonly used in the hand or forearm, and longer catheters inserted into the larger and more central veins of the body. Catheters inserted into these larger veins are known as central lines. Through the IVs the patient receives fluids, drugs, and blood transfusions as needed to support the circulation.

Once the ABC's are secure, life support is directed at maintaining homeostasis, the body's delicate chemical and physical balance. In a healthy person, the body keeps precise control over many components of its makeup, such as its fluids, nutrients, and pressures. When vital organs fail, the body can no longer regulate these components, and the doctor must take steps to restore the normal state.

Preserving the body's internal equilibrium requires careful monitoring of innumerable indicators of the patient's well-being. These indicators include:

  • Vital signs (heartbeats per minute, breaths per minute, blood pressure, body temperature, and weight)
  • Fluids (input and output of the body)
  • Blood cell counts
  • Chemical substances of the body (sodium, potassium, sugar, and many others)
  • Pressures in the circulation, lungs, and perhaps even the brain
  • Presence of germs (bacteria, fungi) causing infection in body systems (lungs, blood, urine)

This intensive monitoring usually takes place in an intensive care unit (ICU) or critical care unit (CCU) and requires:

  • Specialized physicians, such as cardiologists, intensivists, and surgeons
  • Highly-skilled nursing care, often one nurse per patient around-the-clock
  • Extensive support staff, such as respiratory therapists, laboratory technicians, radiology technicians, dieticians, and pharmacists
  • Constant measurement of basics such as pulse, heart rhythm, and oxygen level in the blood
  • Frequent inspection of the patient's alertness, color, and level of pain
  • Use of catheters in the veins and arteries to withdraw blood samples and measure pressures in the circulation
  • Use of tubes in the bladder (Foley catheter), stomach (nasogastric tube), and other body cavities
  • Frequent laboratory tests on blood, urine, drainage from wounds, and other body specimens
  • X-ray, ultrasound, computerized tomography (CT), and other imaging procedures
  • Electrocardiograms

The treatments of life support include:

  • Oxygen
  • Intravenous fluids with sugar and basic salts
  • Drugs to improve circulation and other body functions
  • Antibiotics
  • Transfusions
  • Surgery
  • Nutritional supplements by vein or stomach tube
  • Tubes in body cavities (chest or abdomen) to relieve fluid buildup
  • Dialysis
  • Pacemaker
  • Electrical defibrillation
  • Various machines to assist heart or lung function
  • Transplantation of organs or mechanical substitutes (artificial heart)
  • Sedation or even temporary paralysis to enable the patient to tolerate these procedures

Preparation

The need for life support may arise suddenly and with little warning. All people should discuss in advance with family and doctor their wishes for the use of life support should a medical crisis develop. The doctor will note the preferences in the patient's record. Patients should sign documents such as an Advance Directive and Durable Power of Attorney for Health Care to express their wishes and designate a surrogate decision-maker in case of incapacitation.

Physicians and medical care providers must anticipate the possibility that a patient will require life support, perhaps suddenly. In preparation, doctors and medical staff must:

  • Receive training in resuscitation skills
  • Monitor patients carefully
  • Maintain proper supplies and equipment
  • Discuss in advance with patients and patients' families whether or not to begin life support

Aftercare

If a patient survives life support treatments, doctors will cautiously try to wean the patient from the support systems. Being able to breathe adequately without the ventilator is one major hurdle. Patients commonly fail in their first attempts to breathe on their own, often tiring out after a few hours. Thus, the doctor will reconnect the ventilator, give the patient a rest, and try again in a day or two.

As the patient regains organ function, there is less need for monitors, tests, and treatments that require an intensive care setting. The doctor may transfer the patient to a lower level of hospital care, a skilled nursing facility (SNF), or perhaps directly to home. Physical and occupational therapists may help the patient improve strength and endurance. The patient will receive continuing care from the primary doctor and specialists as needed. The patient may require prescription drugs, assist devices, and psychological therapists.

Risks

The risks and consequences of life support are enormous. These risks include:

  • Physical dangers
  • Emotional suffering
  • Financial costs
  • Societal discord

The physical dangers of life support encompass all the hazards of the patient's underlying disease and treatments. Among these risks are:

  • Permanent damage to the brain, kidneys, and other vital organs caused by poor circulation or low oxygen content of the blood
  • Direct damage to organs from use of medical instruments and procedures
  • Infections, often with organisms that are highly resistant to antibiotics
  • Abnormal blood clots
  • Skin ulcers from lying immobilized for long periods
  • Extreme pain
  • Exposure of medical personnel to communicable diseases

The emotional consequences of life support touch patients, families, and medical caregivers. These repercussions arise from:

  • The frightening environment of an ICU
  • The need to make life-and-death decisions
  • The anger, guilt, and grief that relate to life-threatening illness
  • The fact that many lengthy and difficult treatments will end in failure

The financial costs of life support are huge. A single day of life support costs many thousands of dollars. These expenses fall on individual payers, insurance companies, health plans, and governments. All such payers face difficult decisions regarding the allotment of money for such treatment, especially in cases that are likely to be futile.

Society as a whole faces difficult decisions surrounding life support. Some governments have enacted regulations that establish priorities for the spending of health care resources. Patients who do not receive treatment under such rules may feel victimized by society's choices.

KEY TERMS

Cardiopulmonary Relating to the heart and lungs.

Central line A tube placed by needle into a large, central vein of the body.

Coma Unconsciousness.

Defibrillation Use of an electric shock to restore a normal heartbeat.

Endotracheal tube A tube placed into the wind-pipe through the nose or mouth.

Foley catheter A tube that drains urine from the bladder.

Homeostasis The internal chemical and physical balance of the body.

Nasogastric tube A tube placed through the nose into the stomach.

Neuromuscular Relating to nerves and muscles.

Resuscitation Treatments to restore an adequate airway, breathing, and circulation.

Sepsis An overwhelming infection with effects throughout the body.

Tracheotomy A surgical procedure in which a tube is inserted into the trachea through an incision made in the base of the throat.

Trauma Serious physical injury.

Ventilator A machine that pumps air in and out of the lungs.

Vital signs Basic indicators of body function, usually meaning heartbeats per minute, breaths per minute, blood pressure, body temperature, and weight.

Resources

BOOKS

Irwin, Richard S., Frank B. Cerra, and James M. Rippe, editors. Irwin and Rippe's Intensive Care Medicine. Philadelphia: Lippincott-Raven, 1999.

Luce, John M., "Approach to the Patient In a Critical Care Setting." In Textbook of Medicine, edited by Lee Goldman and J. Claude Bennett, 21st ed. Vol. 1. Philadelphia: W.B. Saunders Company, 2000, pp. 483-4.

Tintinalli, Judith E., et al, editors. Emergency Medicine: a comprehensive study guide. New York: McGraw-Hill, 2000.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Life Support." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"Life Support." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/life-support

"Life Support." Gale Encyclopedia of Medicine, 3rd ed.. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/life-support

Life Support System

Life Support System

The phrase "life support" refers to the medications and equipment used to keep people alive in medical situations. These people have one or more failing organs or organ systems, and would not be able to survive without assistance. The organs and organ systems that often fail and require life support are breathing (respiratory system); heart and blood pressure (cardiovascular system); kidney (renal system); and intestines (gastrointestinal system). The brain and spinal cord (central nervous system) may also fail, but in this case life support is directed at keeping the other body systems functioning so that the nervous system has time to return to a state where it can again support the other body functions. The most common types of life support are for the respiratory, cardiovascular, renal, and gastrointestinal systems.

Respiratory System

Oxygen is the basic method for improving the function of lungs. When the lungs do not function properly because they cannot transmit the oxygen across the lung to the blood, or internal temporary (asthma) or permanent (emphysema) changes make the lungs work inefficiently, adding oxygen may often overcome the defect. The problem usually resides in the lungs, but is sometimes in the blood's oxygen carrying capacity, such as in some poisonings.

In the case of severe illnesses or injuries, oxygen alone may not be sufficient. Often the mechanical problem is so severe that, to keep the person alive, a machine must assume the work of breathing. While patients in these situations may temporarily be sustained when a health care professional forces air into their lungs using a bag-valve mask, they will nearly always need a tube placed into their trachea (endotracheal tube) before they are placed on a ventilator. The clear polyvinyl endotracheal tubes can be placed through the mouth in most cases or the nose. Shorter tracheostomy tubes serve the same purpose and are placed surgically, through incisions in the front of the neck. Both can be initially connected to bags that are squeezed to help the patient breath. Patients are then placed on ventilators.

Ventilators are machines that push oxygenated, humidified, and warmed air into the lungs. These sophisticated machines monitor, among other things, the amount of oxygenated air flowing into the patient with each breath, the pressure needed to deliver that amount of air, and the resistance in the patient's lungs. Patients nearly always need medications to help them tolerate being on a ventilator. These include drugs that induce reversible paralysis, sedatives, and, when necessary, analgesics.

Special ventilators are sometimes used for children, and premature neonates now receive surfactant, which are medications that reduce alveolar surface tension, to help their lungs remain open while they develop. Adults with life-threatening spasms in their airways receive medications to reverse or prevent them.

When a lung collapses, or when blood or fluid fills a patient's chest outside the lung (pleural space) so that breathing becomes difficult, clinicians place a tube (chest or thoracostomy tube) through the chest wall to drain the fluid or air and to re-expand the lung.

Cardiovascular System

The most common method to support patients with life-threatening abnormalities of the heart or blood vessels (cardiovascular system) is with medications. These include the vasopressorsused to raise the blood pressure and antiarrhythmics used to slow, increase, or normalize the heart's rhythm. Other medications used to stabilize the cardiovascular system in life-threatening situations include antihypertensives, used to lower severely high blood pressure when organs are suffering severe damage, such as during a stroke or heart attack, and diuretics to drain excess fluid from the body so that the heart has less work to do.

The heart can be mechanically assisted to function normally. Patients with life-threatening heart rhythms can be cardioverted (shocked with electricity) back into a normal rhythm. Sometimes a temporary cardiac pacemaker must be placed when the heart's electrical system fails. Patients may also be placed on either a partial or complete mechanical system to support the heart. One of several partial systems, the Left Ventricular Assist Device, is passed through a groin artery to temporarily assume some of the heart's work until it can regain its ability to function independently. Patients sometimes go on a heart-lung bypass machine (aside from surgery) in order to maintain their heart while they are treated. Some centers also use artificial hearts, usually to maintain patients until they can receive a permanent heart transplant.

If sufficient fluid collects around the heart, it can decrease the heart's ability to function. In those cases, clinicians must perform pericardiocentesis, drawing fluid off so the heart again functions. If the heart stops, clinicians perform cardiopulmonary massage or open-chest cardiac massage in an attempt to restore an effective cardiac rhythm.

Renal System

The renal system (kidneys, ureters, and bladder) can fail acutely, causing a threat to life. Many of these patients can only be kept alive through using an artificial kidney system, known as dialysis. In some cases, this may only be used for a short time; for many patients, they spend the rest of their livesor until they receive a kidney transplant on this artificial blood-cleansing system. Patients can use either peritoneal dialysis or hemodialysis. Peritoneal dialysis involves instilling into and withdrawing from the abdomen liters of special dialysate (water with a careful mixture of chemicals) each day. Hemodialysis, usually performed three times a week at special centers, uses a shunt, usually in an extremity, to connect the patient to a hemodialysis machine.

Gastrointestinal System

Many patients on life support cannot take in enough calories to sustain themselves, even if they can eat. They receive artificial nutrition and hydration, essentially medically instilled supplements, to keep them alive. These may be given through nasogastric tubes for a limited period of time. Many receive this therapy through central lines (long catheters passing into the larger veins), gastrostomyn tubes, or similar surgically placed devices.

Other Types of Life Support

Life support may also include blood and blood product transfusions and many types of drugs. Many patients receive insulin, sometimes as insulin drips, if they are in diabetic crisis. Other patients, especially those with cancers affecting their spinal cord or bone marrow, may receive emergency anticancer drugs or radiation therapy.

Futility and Trials of Therapy

Clinicians may use life support appropriately or inappropriately. The most common appropriate use is to maintain patients long enough so that the individuals' organ systems return to a life-sustaining level of function. In some cases, such as patients with degenerative neurological diseases (i.e., amyotrophic lateral sclerosis, commonly called Lou Gehrig's Disease) or kidney failure, support for a failing organ may become chronic. In the former case, patients may elect to be placed on ventilators to support their breathing, while in the latter they usually receive dialysis.

Life support is often used inappropriately to maintain patients beyond the point at which it is clear that they have no chance of recovery, sometimes called "futile treatment." Such patients often have failure in multiple organ systems and one or more severe underlying diseases. Futile and medically inappropriate interventions may violate both the ethical and medical precepts generally accepted by patients, families, and physicians. Most of those who receive such futile treatment are elderly, although futile treatment seems to be more common among the much smaller number of young people dying in hospitals. As shown by Rivera and colleagues, families are responsible for continuing futile treatment in the majority of cases, although it is sometimes accompanied by family dissent over the right course of action. Physicians continue futile treatment in only about one-third of such cases, sometimes because of liability fears. Unreasonable expectations for improvement were the most common underlying factor. Bioethics consultations can often resolve issues of unwanted or non-beneficial medical treatments.

To be on life support the patient must still be alive. However, these systems may be used to maintain the body of an individual who has been declared dead by brain criteria (brain dead) until critical organs, such as the heart, lungs, liver, kidneys, and pancreas, can be recovered in the operating room. Occasionally these systems are also continued for such a patient until families arrive or until they have come to terms with the death. In these cases, however, they are simply called support rather than life support.

When patients are recovering and as long as they or their surrogate decision makers want medical treatments, continuing life support is appropriate. When it becomes unclear whether the treatment will be of benefit, it is often appropriate for the family (or patient) and the clinician to use a time-limited trial of therapy. This is a decision to use life support for a specific period of time; if there is no improvement at that point, everyone agrees that the support will be stopped.

See also: Advance Directives; Cruzan, Nancy; Persistent Vegetative State; Quinlan, Karen Ann; Resuscitation; Suicide Types: Physician-Assisted Suicide

Bibliography

Iserson, Kenneth V. Death to Dust: What Happens to Dead Bodies? 2nd edition. Tucson, AZ: Galen Press, 2001.

Iserson, Kenneth V. Grave Words: Notifying Survivors about Sudden, Unexpected Deaths. Tucson, AZ: Galen Press, 1999.

Rivera, Seth, Dong Kim, Shelley Garone, Leon Morgenstern, and Zab Mohsenifar. "Motivating Factors in Futile Clinical Interventions." Chest 119 (2001):19441947.

KENNETH V. ISERSON

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Life Support System." Macmillan Encyclopedia of Death and Dying. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"Life Support System." Macmillan Encyclopedia of Death and Dying. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/social-sciences/encyclopedias-almanacs-transcripts-and-maps/life-support-system

"Life Support System." Macmillan Encyclopedia of Death and Dying. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/social-sciences/encyclopedias-almanacs-transcripts-and-maps/life-support-system

Life Support

Life Support

Human space exploration is a critical aspect of space sciences. Although robotic probes are invaluable for preliminary studies or high-risk environments, humans are able to solve problems, improvise, and make discoveries that are not programmed into a probe's software. Keeping astronauts safe and healthy while in space is a major concern. Non-astronauts take for granted many of the life support concerns that astronauts must consciously address to ensure their mission's success. Variables include gas requirements, temperature, gravity, radiation, and pressure. Waste products must be carefully monitored, and disposal or recycling must be planned. When astronauts leave Earth, many plans, procedures, and backup systems are in place for their comfort and survival.

Temperature

During a space mission, astronauts and their spacecraft are exposed to temperature extremes on both ends of the scale. On the Moon, for example, when the Sun is up, the surface temperature can go as high as 243°F (117°C) but at night it can drop to -272°F (-169°C). This was a major concern for the Apollo Moon missions.

The vacuum of space is extremely cold and deadly to unprotected human life. However, the heat felt during liftoff and re-entry through the atmosphere is intensely hot. Engineers must design space suits that keep astronauts warm when they embark on space walks in the extreme cold of space. They must also design heat shielding for the space shuttle that will withstand the high temperatures of re-entry into Earth's atmosphere. For example, after the shuttle has entered orbit, the cargo bay doors open to help release much of the pent-up heat created during liftoff and ascent. Conversely, the shuttle must be pointed at a appropriate angle and rotation to ensure that the heat of re-entry is distributed properly against specially reinforced, heat-resistant panels. During re-entry, the space shuttle will encounter incredibly hot temperaturesup to 3,000°F. This requires the shuttle to be equipped for the temperature extremes.

Gravity and Microgravity

During liftoff, the effects of gravity on the human body are intense and cause physical discomfort. Astronauts are tested in simulators to ensure they can survive the gravitational effects of space shuttle liftoff, which are up to three times that of Earth gravity.

Once in space, astronauts must adapt to microgravity, a nearly weightless environment. Human bodies are accustomed to the amount of gravity experienced on Earth, where muscles and bones are always competing with gravity. But in space, astronauts lose bone and muscle mass. Their hearts do not have to beat as hard or as fast to make blood pump through the body. Despite a rigorous exercise schedule while in space, nearly all astronauts exhibit muscle and bone deterioration after spaceflights of significant duration.

Other Survival Concerns

Humans bodies take in food, water, and oxygen necessary for life, and then produce wastes as liquids, solids, and carbon dioxide. Space missions must ensure an adequate supply of life-sustaining resources for the journey, as well as a safe way of disposing of waste products. Recycling is important in space, and both technological and biological equipment are used. Many different ways of waste product disposal have been used and or studied by NASA. These methods include space jettison , plant fertilizers, and technology that filters and cleans the waste to allow useful materials to be reused.

Extra vehicular activity (EVA) suits, protect astronauts in the vacuum of space. These suits protect against extreme cold, radiation, and help recycle carbon dioxide into oxygen. However, just as the space shuttle has its limitations, these suits do as well. Their life support systems can be overwhelmed, requiring that they be used for only short periods of time, such as space walks. During space walks, MMUs (Manned Maneuvering Units) have been used as a means of moving small distances. The MMUs are similar to jetpacks for the astronauts. They allow small bursts of propulsion thrusters to be fired from the pack, allowing astronauts to change their direction and momentum.

One commonly forgotten life support concern is the energy required for all of the spacecraft's equipment. The space shuttle must have failsafes to ensure that there will be enough energy for the onboard computer systems, just as there must be sufficient fuel. These energy sources are as important as any other because without them, the mission would not be feasible. Extensive research is underway to try and use new, cheaper fuels in future human space exploration missions.

see also Living in Space (volume 3); Manned Maneuvering Unit (volume 3); Space Walks (volume 3).

Craig Samuels

Bibliography

Davis, Amanda. Exploring Space: Space StationsLiving and Working in Space. New York: Rosen Publishing, 1998.

Sulzman, Frank M., and Albert M. Genin, eds. Space Biology and Medicine, Vol. 2: Life Support and Habitability. Reston, VA: American Institute of Aeronautics and Astronautics, 1994.

Internet Resources

Advanced Life Support and Gravitational Biology at Kennedy Space Center. NASA Kennedy Space Center. <http://bioscience.ksc.nasa.gov/oldals/>.

Advance Life Support: NASA Johnson Space Center. NASA Johnson Space Center.<http://advlifesupport.jsc.nasa.gov>.

Lifting Bodies See Hypersonic Programs (Volume 3).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Life Support." Space Sciences. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"Life Support." Space Sciences. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/science/news-wires-white-papers-and-books/life-support

"Life Support." Space Sciences. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/news-wires-white-papers-and-books/life-support

life support

life sup·port • n. Med. maintenance of the vital functions of a critically ill or comatose person or a person undergoing surgery: [as adj.] a life-support machine. ∎ inf. equipment in a hospital used for this: a patient on life support.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"life support." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"life support." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/life-support

"life support." The Oxford Pocket Dictionary of Current English. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/life-support

life support system

life support system: see artificial life support; Life Support for Human Spaceflight under space science.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"life support system." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"life support system." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/life-support-system

"life support system." The Columbia Encyclopedia, 6th ed.. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/life-support-system