What is Basic Life Support?

Basic life support (BLS), also known as basic cardiac life support, is a care process that is initiated when someone experiences sudden cardiac arrest (SCA), respiratory distress, or an obstructed airway. It can be performed by lay people, trained bystanders, or certified first responders, and should be put into effect immediately following one of these events.

Activating the Chain of Survival for Basic Cardiac Life Support

If a bystander witnesses someone who may be experiencing SCA, they should employ the chain of survival. The chain of survival comprises six critical actions that can help increase a victim’s chances of surviving SCA and other life-threatening emergencies.

According to the 2020 American Heart Association (AHA) Guidelines for CPR and Emergency Cardiovascular Care, a bystander should perform the first three steps of the chain of survival right away:

  • Recognize the emergency by activating the emergency response system — If you witness a sudden collapse followed by a loss of consciousness, call 911 immediately and begin the BLS process. Ask another bystander to find a nearby AED.
  • Immediately begin performing high-quality CPR — Begin chest compressions at a rate of 100–120 compressions per minute and at a depth of 2–2.4 inches.
  • Provide rapid defibrillation — When the AED arrives, attach the pads to the victim's bare chest, turn the device on, and follow the prompts. If needed, the AED will administer a shock.

The final three steps of the chain of survival (initiate advanced life support, provide post-cardiac arrest care, and provide long-term recovery support) must be performed by a medical professional.

The AHA has also provided practical guidance to help untrained rescuers perform BLS. Upon witnessing an event that may be SCA, follow these steps:

  • Ensure scene safety.
  • Check for response.
  • Ask a bystander to call emergency services. If no bystanders are nearby, call emergency services yourself.
  • Check the victim’s breathing. If they are not breathing or are gasping, ask the dispatcher for guidance on how to respond.
  • Follow the dispatcher’s instructions.

Note that there are special circumstances that may call for altered BLS practices. More detail can be found in Part 3 of the 2020 American Heart Association Guidelines for CPR and ECC.

Sources for Basic Life Support Training

Basic life support training courses are often geared toward pre-hospital personnel, such as EMTs, paramedics, and firefighters. However, any layperson or professional who would like to help save lives can and should take a BLS course.

Reputable BLS courses are offered by the following organizations:

  • The American Heart Association — The AHA offers both self-directed and instructor-led courses.
  • American Red Cross — The ARC offers in-person and hybrid training. BLS training options are designed for different groups, including healthcare professionals, workplaces, and general audiences.