Basic Life Support (BLS)

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Author: Margaret Alic
Editor: Brigham Narins
Date: 2013
The Gale Encyclopedia of Nursing and Allied Health
Publisher: Gale, a Cengage Company
Document Type: Topic overview
Pages: 5
Content Level: (Level 4)

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Page 425

Basic Life Support (BLS)


Basic life support (BLS) refers to emergency procedures and treatments for life-threatening illness or injuries until advanced medical support is available. BLS includes relief from choking , the staunching of bleeding, basic first aid , and cardiopulmonary resuscitation (CPR) , and use of an automated external defibrillator (AED). Sometimes additional medical procedures—such as supplying oxygen, mechanical ventilation to maintain respiration, or the administration of fluids, blood products, or emergency medications—are also referred to as BLS. BLS also may refer to the administration of oxygen, hydration, and nutrition to maintain life.


BLS can save lives in a variety of circumstances involving isolated accidents and sudden illnesses, as well as natural disasters, warfare, and public emergencies with multiple casualties. Situations requiring BLS can include:

  • sudden cardiac arrest
  • strokePage 426  |  Top of Article
  • drowning
  • choking
  • accidental injuries
  • violence
  • severe allergic reactions (anaphylaxis)
  • burns
  • hypothermia
  • birth and newborn complications
  • drug overdoses
  • alcohol intoxication

Cerebral hypoxia—insufficient oxygen reaching the brain due to heart or respiratory failure—is the most common situation requiring BLS. Cerebral hypoxia can be caused by cardiac arrest, drowning, choking, strangling, suffocation, head trauma, carbon monoxide poisoning , or complications of general anesthesia . In the United States, there are about 300,000 cardiac arrests occurring outside of hospitals every year. The brain can be irreparably damaged by oxygen starvation within just a few minutes of cardiac arrest and, without CPR , the victim may die within 8-10 minutes.


BLS is the first or lowest level of medical care. It is followed by advanced life support and critical care. Although healthcare providers and emergency medical technicians are trained to perform BLS, it is often provided at the scene by family members or bystanders, while awaiting an ambulance or emergency personnel. BLS is also provided in the ambulance while on route to a hospital. Equipment and supplies available to emergency personnel for BLS include AEDs, oxygen, fluids, blood products, medications to support blood pressure and heart rate and suppress seizures, and antimicrobial drugs. BLS ambulances include splint treatments and CPR capabilities; however, many ambulances are equipped with equipment for advanced life support. Fire response vehicles also generally carry BLS equipment including AEDs.

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CPR for restoring breathing and circulation is the most common form of BLS. In 2010, the American Heart Association (AHA) changed their guidelines for CPR, in part, to encourage bystanders, regardless of training, to employ basic life support. The guidelines call for using “hands-only” CPR (chest compressions) on adults and children over age eight, without interruption for rescue breaths or other measures. Chest compressions can be performed by most people, even without training, and are at least as effective for cardiac arrest as full CPR. Continuous chest compressions circulate blood through the heart to the brain and other vital organs. Even inexpertly performed chest compressions are more effective than no attempt at resuscitation.

Continuous-chest-compression or hands-only CPR is used for victims who have suddenly collapsed for no obvious reason, are not breathing normally, and are unresponsive, suggesting cardiac arrest, such as may be caused by a heart attack. Trained responders should check for a pulse before initiating chest compressions, but all other responders should begin chest compressions immediately after summoning assistance. Chest compressions should be at least 2 in. (5 cm) deep for adults, at a rate of 100 compressions per minute. The chest should recoil completely between compressions. Chest compressions should be continued without interruption until termination of resuscitative efforts (usually due to the arrival of emergency personnel), the use of an AED, or the return of spontaneous circulation.

Full or conventional CPR is preferable for infants and children under age eight and for collapse due to an inability to breathe. With respiratory arrest, lack of oxygen is the primary concern, although respiratory arrest eventually leads to cardiac arrest. Respiratory arrest is most often caused by choking, drowning, a drug reaction or overdose , alcohol intoxication, a severe asthma attack, carbon monoxide poisoning , or other breathing problems. It is generally not sudden or unexpected. Although cardiac arrest is about 20 times more common than respiratory arrest, respiratory arrest is more common in children. Full CPR utilizes CAB: chest compressions to maintain or restore circulation, airway clearing, and breathing—checking for breath and administering rescue breaths or mouth-to-mouth artificial respiration if necessary. A breathing barrier or CPR mouthpiece are standard components of many first-aid kits.

AED use is considered a part of CPR. Chest compressions alone cannot restore a heartbeat, although they will continue to circulate the blood, albeit weakly. Electrical stimulation with an AED is used to restart the heart or normalize ventricular fibrillation (a rapid, irregular heartbeat). Chest compressions are initiated while waiting for an AED or if a defibrillator is not available. The AED analyzes the heart rhythm and delivers the appropriate electric shock .

Other basic life supports

Depending on the situation, other types of BLS may be required. BLS can involve first-aid measures, such as slowing or staunching bleeding or scraping a bee stinger Page 427  |  Top of Articleoff the skin in a case of a severe allergic reaction. A foreign object may need to be removed from a child's mouth, and choking can be treated with the Heimlich maneuver .

Other BLS measures may include:

  • mechanical ventilation for breathing assistance
  • intravenous epinephrine to restore heartbeat
  • medications for a slow or unstable heartbeat
  • fluids, blood products, and medications to raise and maintain blood pressure and heart rate
  • medications such as phenytoin, phenobarbital, valproic acid, or general anesthetics to suppress seizures
  • oral or injected emergency allergy medications


A pillow should never be placed under the head of a victim who is having trouble breathing, since this can block the airways. Likewise, a victim who is having trouble breathing should never be given anything by mouth, including oral medications, since this can block the airways. When employing a chin lift or jaw thrust to clear an airway, care must be taken to avoid extending the neck in cases where there could be a cervical spinal injury.

CPR recommendations evolve, as further research and increased experience indicate the best ways to save lives. CPR assistance devices, other than AEDs, are generally not recommended. Furthermore, although AEDs have significantly increased survival rates, approximately 76% of cardiac arrests do not respond to electric shock, and chest compressions are required for the survival of these patients. Furthermore, chest compressions applied within 20 seconds before and after defibrillator shocks increase survival chances by more than 50% compared with longer delays between chest compressions and defibrillation . Unfortunately, even successful CPR often fails to prevent irreversible damage to the brain and other organs.


BLS requires first recognizing a life-threatening situation. The victim may have to be moved from a dangerous scene or situation before BLS can be administered. Bystanders should call 911 or another emergency number. A conscious victim should be calmed and reassured. Finally, all homes and vehicles should have well-stocked first-aid kits.

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In the case sudden collapse, the first response is usually “check and call.” The scene is checked for hazards that require moving the victim, and then the victim is checked. If the victim appears unconscious, the rescuer taps or shakes the victim on the shoulder and asks loudly “are you okay?” The rescuer checks for breathing by kneeling by the victim's shoulders and placing his or her cheek next to the victim's mouth to observe any signs of breath in the chest and abdomen and listen and feel for signs of breath through the mouth. If the victim is unresponsive, someone else should call 911 while the rescuer begins CPR. If the rescuer is alone and has immediate access to a telephone, 911 should be called before initiating CPR, unless the victim is an infant or young child or it is a case of apparent respiratory arrest. In the latter cases, CPR should be performed for one minute before calling for help.

The universal mnemonic for CPR preparation is ABCD:

  • Airway—is the airway open?
  • Breathing—is the victim breathing?
  • Circulation—does the victim have a pulse or signs of blood circulation?
  • Defibrillation—where is the defibrillator?

Increasingly, fire stations, emergency vehicles, airports, airplanes, shopping malls, and even private homes have AEDs onsite with user-friendly instructions. The devices are equipped with prompts, but a 911 or other emergency operator may also be able guide a rescuer in the use of an AED.


Everyone—not just emergency responders and healthcare professionals—should be trained in BLS, including first aid and CPR. BLS training is particularly important for parents, caregivers, teachers, babysitters, and those who live with someone at risk of cardiac or respiratory arrest. CPR, first-aid, and BLS courses for the public are available at hospitals, community centers, fire and rescue departments, and at other organizations, including churches, workplaces, and senior centers. The AHA, local American Red Cross chapters, YMCAs, YWCAs, recreation and aquatic centers, and public health agencies also offer CPR classes. They include hands-only and full CPR and use of an AED. Classes usually last one to several hours and are often free. Trainings should be repeated every two years, although many people attend on an annual basis to refresh their skills. Various online and video trainings are also available. Walk-through CPR instructions based on AHA guidelines are available as smart phone applications.

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The AHA offers BLS classes for healthcare professionals, both in various hospital and out-of-hospital settings and online. The web-based classes use case studies and scenarios, interactive activities, and videos. The courses cover BLS for both individual rescuers and teams. They are designed to provide all members of the healthcare team with the capability to recognize life-threatening emergencies, relieve choking, perform CPR, and use an AED in effective, timely, and safe ways.


Emergency medical care is always required following BLS. While awaiting emergency help, victims should be laid flat, with their feet raised about 12 in. (30 cm), and covered with a coat or blanket. However, a victim should never be placed in this position if a head, neck, back, or leg injury is suspected or if the position causes discomfort. If normal breathing and heartbeat are restored with CPR, the victim should be turned on his or her side, made comfortable, and kept still until emergency medical personnel arrive. The rescuer should speak positively and reassure the victim that help is on the way.


Although CPR saves thousands of lives, it often fails to save the victim's quality of life. Although breathing and heartbeat may be restored, damage resulting from loss of oxygen to the brain is not uncommon. Successful CPR may leave a cardiac arrest victim in a coma . CPR also can injure the victim's ribs, liver , lungs , and heart.

Another complication of BLS arises from future directives with “do not resuscitate” clauses or requesting the withholding of basic life support, including artificial feeding and hydration, under specific circumstances.

Sidebar: HideShow


A universal mnemonic—Airway, Breathing, Circulation, Defibrillation—for preparing to perform CPR.
Severe, potentially fatal hypersensitivity caused by exposure to an allergen following a previous exposure, which can result in blood vessel dilation and a sharp drop in blood pressure, smooth muscle contraction, and difficulty breathing.
Automated external defibrillator; AED—
A device that analyzes heartbeat and automatically delivers an appropriate electric shock to restart the heart or to correct heart fibrillation.
Basic cardiac life support (BCLS)—
Life support for sudden cardiac arrest; training and certification in BCLS is required of most healthcare workers.
The American Heart Association's acronym for CPR steps—Circulation, Airway, Breathing.
Cardiac arrest—
Abrupt cessation of the heartbeat or sudden switch to fibrillation.
Cardiopulmonary resuscitation; CPR—
An emergency procedure for restoring circulation and breathing.
Cerebral hypoxia—
A lack of oxygen in the brain.
Restoring rhythm to a fibrillating heart, as with an electric shock.
Very rapid, irregular heart contrac-tions.
First aid—
Treatment of minor injuries or conditions or immediate care or treatment for a medical emergency that is administered while awaiting assistance.
Full CPR—
Conventional CPR that includes chest compressions, airway clearing, and rescue breaths.
Hands-only CPR—
Continuous-chest-compression CPR; chest compressions without rescue breathing.
Heimlich maneuver—
The application of sudden upward pressure on the upper abdomen to force a foreign object from the trachea of a choking victim; developed by the American surgeon Henry Jay Heimlich.
Rescue breath—
Mouth-to-mouth resuscitation, which is combined with chest compressions in full CPR.
Respiratory arrest—
Cessation of breathing due to failure of the lungs to contract.
Reviving after apparent death.
A sudden diminishing or loss of consciousness, sensation, or voluntary movement from a rupture or obstruction of a blood vessel in the brain.


Basic life support saves many lives. Approximately 92% of victims of sudden cardiac arrest die before reaching a hospital; however, immediate CPR can double Page 429  |  Top of Articleor triple their chances of survival. Nevertheless, bystander CPR is performed in only about 25% of such incidents.

Healthcare team roles

All healthcare providers, emergency responders, and staff of healthcare facilities are expected to be trained in pediatric and adult BLS. Certified midwives are trained in BLS for newborns. Most healthcare facilities require workers to be certified in Basic Cardiac Life Support (BCLS), which includes CPR. Healthcare workers should also emphasize to their patients the importance of CPR training.

Healthcare professionals aiding a victim in an emergency situation are legally protected from liability under the U.S. Good Samaritan Law. This law requires that the situation be an emergency, that there is no monetary compensation for the treatment, and that the care is provided “in good faith.” However in most states, healthcare professionals are not under mandatory obligation to provide BLS in an emergency situation.

Sidebar: HideShow


  • Should I take a basic life support (BLS) course?
  • What will I learn in a BLS class?
  • What supplies should I have on-hand for BLS?
  • Should I practice hands-only CPR or full CPR?
  • Should I purchase a defibrillator for my home?



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American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231, USA(800) AHA-USA-1 (242-8721),

U.S. Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333, USA(800) CDC-INFO (232-4636),, .

Margaret Alic, PhD

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Gale Document Number: GALE|CX2760400129

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.