Taking the right action quickly and confidently can make the difference between life and death for a person dealing with cardiac arrest!

General Concepts of Basic Life Support

According to the Centers for Disease Control (CDC), heart disease continues to be the leading cause of death in the United States. Research continues to improve how we respond with life-saving techniques to emergencies. These techniques are organized into a systematic response called the Chain of Survival, which begins with Basic Life Support (BLS). The Chain of Survival provides the victim the best chance to receive the care needed and return to a healthy life.


The heart pumps blood through the lungs, where blood takes in oxygen and releases carbon dioxide. This blood then returns to the heart and is pumped to vital organs. When the heart stops, blood flow stops, and the person quickly becomes unconscious. Without blood flow, the heart and the brain soon become damaged due to a lack of oxygen. The actions that make up BLS try to prevent or slow the damage until the cause of the problem can be corrected. BLS improves a person’s chance of surviving until advanced care becomes available.

Keys for BLS:

  • Quickly start the Chain of Survival.
  • Deliver high-quality chest compressions to circulate oxygen to the brain and vital organs.
  • Know when and how to use an Automated External Defibrillator (AED).
  • Provide rescue breathing.
  • Understand how to work with other rescuers as part of a team.
  • Know how to treat choking.

Initiating Chain of Survival

Early initiation of BLS has been shown to increase the probability of survival for a person in cardiac arrest. The rescuer should follow the Adult Chain of Survival steps to increase the odds of surviving a cardiac event. The steps vary based on out-of-hospital cardiac arrest vs. in-hospital cardiac arrest.

The American Heart Associations AHA Adult Chain of Survival.

BLS for Adults


  • Check for the carotid pulse on the side of the neck and look for breathing. 
    • Remember not to waste time trying to feel for a pulse; feel for no more than 10 seconds. If you are not sure you feel a pulse, begin CPR.
  • Start chest compress
    • Use the heel of one hand on the lower half of the sternum in the middle of the chest.
    • Put your other hand on top of the first hand.
    • Straighten your arms and press straight down. 
    • Compressions should be 2 to 2.4″ (5 to 6 cm) into the person’s chest and at 100 to 120 compressions per minute.
  • After 30 compressions, stop compressions and open the airway by tilting the head and lifting the chin.
    • Put your hand on the person’s forehead and tilt the head back.
    • Lift the person’s jaw by placing your index and middle fingers on the lower jaw.
  • Give a breath while watching the chest rise. Repeat while giving a second breath. Breaths should be delivered over one second.

  • Resume chest compressions. Switch quickly between compressions and rescue breaths to minimize interruptions in chest compressions.

Stop pressing the chest between each compression and allow the chest wall to return to its natural position. Leaning or resting on the chest between compressions can keep the heart from refilling in between each compression and make CPR less effective.

Do not perform the head tilt/chin-lift if you suspect the person may have a neck injury. In that case, the jaw thrust is used.

For the jaw-thrust maneuver, grasp the angles of the lower jaw and lift it with both hands, one on each side, moving the jaw forward. If their lips are closed, open the lower lip using your thumb.

Automated External Defibrillator (AED)

Ventricular fibrillation, caused by disorganized electrical activity in the heart’s main pumping chambers, is a common cause of cardiac arrest. The treatment for ventricular fibrillation is defibrillation, or the delivery of an electric shock to the heart through the person’s chest wall. This shock stops the disorganized electrical activity and resumes the heart’s normal rhythm.


The automated external defibrillator (AED) is a device that recognizes ventricular fibrillation and other dysrhythmias and delivers an electric shock at the right time. The AED has become a common sight in public buildings. The AED is nearly foolproof and will not allow you to make a mistake. It is safe for anyone to use. In a witnessed cardiac arrest, where the person is observed to collapse suddenly, the most common cause is likely to be ventricular fibrillation, and a defibrillator should analyze the person’s cardiac rhythm as soon as possible.

Correct AED Pad Placement

BLS for Children 1 – Puberty

Many similarities exist between the BLS guidelines for Adults and Children. The main differences between the two are:

  • For children, the compression-to-breath ratio is 30:2 for one rescuer and 15:2 for two rescuers for all age groups.

  • The depth of compression may be different. For a child, compress the chest at least one-third of the depth of the chest. This may be less than two inches for small children but approximately two inches for larger children (4-5 cm).

  • In children, primary cardiac events are not common. Respiratory problems most commonly precede cardiac arrest. Survival rates improve with early intervention for respiratory issues. Remember that prevention is the first link in the Pediatric Chain of Survival.

Emergencies in children and infants are not usually caused by the heart. Children and infants most often have breathing problems that trigger cardiac arrest. The first and most important step of the Pediatric Chain of Survival is prevention.

AHA Pediatric Chain of Survival

BLS for Infants (0 to 12 months old)

BLS for children and infants is similar. The following are the main differences between BLS for children and BLS for infants:

  • Check the pulse in the infant using the brachial artery on the inside of the upper arm between the infant’s elbow and shoulder.

  • During CPR, compressions can be performed on an infant using two fingers if only one rescuer or with two thumb-encircling hands if there are two rescuers and the rescuer’s hands are big enough to go around the infant’s chest.

  • Compression depth should be one-third of the chest depth; for most infants, this is about 1.5 inches (4cm).

  • In infants, primary cardiac events are not common. Usually, cardiac arrest will be preceded by respiratory problems. Survival rates improve when you intervene with respiratory issues as early as possible. Remember that prevention is the first step in the Pediatric Chain of Survival.
brachial pulse infant CPR
encircling thumbs infant CPR
Two Finger Infant CPR

Automated External Defibrillator (AED) Infants & Children

An AED can be used on infants and children. They should be used as early as possible for the best chance of improving the chance of survival. Check the AED when it arrives at the scene. Pediatric pads should be used if the person is under eight years old or under 55 pounds (25 kg). Standard (adult) pads may be used if pediatric pads are unavailable. Do not let the pads touch if using standard (adult) pads. A manual defibrillator should be used if available for infants under a year old. If a manual defibrillator is not available, an AED may be used. Some AEDs have a switch that can be set to deliver a pediatric shock. If the AED cannot deliver a pediatric shock, an adult shock should be given. It is important to remember that an electric shock may treat a fatal heart rhythm.

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