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    What is the BLS CPR Algorithm?

    Dr. Mary Williams, RN, DC

    About the author

    Dr. Mary Williams, RN, DC

    Dr. Mary Williams, R.N., D.C is a Doctor of Chiropractic with an extensive background as a Registered Nurse and experienced Core Instructor for the American Heart Association. She has over 30 years of hands-on medical and instructional experience.

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    The BLS CPR algorithm is the basic protocol for performing CPR to an unresponsive victim. It’s the definition of high-quality, effective-as-possible CPR.

    There are several different versions of this protocol. Medical professionals get a more complicated version than laypeople, and there are also different versions for adult and pediatric care. However, here are the parts of the algorithm that apply to everyone:

    BLS CPR Algorithm for Healthcare Professionals

    1. Wait no more than 10 seconds to start performing CPR on an unresponsive victim.

    2. The compression rate should be 100-120 compressions per minute. This is about the tempo of “Stayin’ Alive” by the Bee Gees.

    3. The depth of compression should be 2-2.4 inches for adults, about 2 inches for children aged 1 to adolescence, and 1.5 inches for babies.

    4. Let the chest recoil completely after every compression.

    5. Once you start giving CPR, don’t stop if possible—any interruptions to chest compressions should be minimized.

    6. If you’re administering an AED shock, the pause between the last compression and the shock—and the pause between the last shock and the next compression—should be kept to under 10 seconds.

    7. When delivering CPR, start chest compressions before rescue breathing. You should give a rescue breath after your first 30 compressions.

    8. Watch the rise of the chest to see if your rescue breaths were effective.

    9. Avoid any excess ventilation; this could result in vomiting, pneumonia, or aspiration.

    BLS CPR Algorithm for Laypeople (Non-Medical Professionals)

    The version for laypeople is a bit simpler, and emphasizes different things. Here are the details:

    1. Check the victim’s responsiveness. If they are not breathing or not breathing normally—for instance, if they are gasping for breath—start CPR.

    2. Call 911.

    3. Get an automatic external defibrillator (AED), if there is one available.

    4. The algorithm goes in a loop: CPR, rhythm check, and defilation.

    5. Check the pulse before starting chest compressions for at least five seconds and no more than 10 seconds. If you can’t find a pulse or can’t tell if there is one, start compressions.

    6. Push hard and fast in the center of the chest. Start chest compressions before rescue breathing; the ratio is 30 compressions to 2 rescue breaths. Let the chest recoil between compressions.

    7. Chest compressions should be performed at a depth of 2-2.4 inches in adults, and at a rate of 100-120 per minute.

    8. For rescue breathing, deliver 10 breaths per minute or one breath every six seconds. Each breath should last about one second; watch for the chest to ride to determine effectiveness. Avoid excessive ventilation.

    9. Use the AED when you have one available. Use it to check the rhythm, then deliver a shock once every two minutes or five cycles.

    This version includes rescue breaths and use of an AED, but the simplest form of CPR for laypeople is hands-only. All you do is push hard and fast in the center of the chest, to the tune of “Stayin’ Alive” by the Bee Gees.

    Hands-only CPR has been found to be just as effective as the traditional variety when delivered by laypeople; in some circumstances, it’s even more effective.


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