What is the AHA adult basic life support (BLS) algorithm?

Updated: Sep 15, 2020
  • Author: Catharine A Bon, MD; Chief Editor: Kirsten A Bechtel, MD  more...
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In the AHA 2015 guidelines, the adult basic life support (BLS) algorithm has been modified to reflect the widespread use of mobile telephones that can be used for assistance without leaving the patient. The algorithm is detailed in Table 2, below. [43]

Table 2. Adult BLS Algorithm (Open Table in a new window)


Untrained Lay Responders

Trained Lay Responders

Healthcare Professionals

Step 1

Ensure scene safety

Step 2

Check for response

Step 3

Responder should shout for nearby help and phone or have another bystander phone 9-1-1; the phone should remain on speaker for receiving further instructions from the dispatcher.

Responder should shout for nearby help and activate the emergency response system (9-1-1, emergency response). Ensure that the phone remains on speaker, if at all possible.

Responder should shout for nearby help. The resuscitation team can be activated before or after checking breathing and pulse.

Step 4

Follow dispatcher’s instructions.

Check for no breathing or only gasping; if there is none, begin CPR with chest compressions.

A check for no breathing or only gasping and a check of pulse ideally should be done simultaneously. Activation and retrieval of the AED/emergency equipment by either the lone healthcare provider or by a second person must occur immediately after the check of breathing and pulse identifies cardiac arrest.

Step 5

As instructed by dispatcher to check for no breathing or only gasping.

Answer dispatcher’s questions and follow subsequent instructions.

CPR begins immediately, and the AED/defibrillator is used if available.

Step 6

Dispatcher’s instructions are followed.

Send another person for an AED, if one is available.

With arrival of a second responder, two-person CPR is provided and AED/defibrillator is used.

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