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CPR alone rarely saves lives: some statistics

Statistically, CPR without an Automated External Defibrillator (AED) only works 3% to 4% of the time. (A 1996 study by the New England Journal of Medicine showed that in television shows CPR was portrayed as successful 75% of the time.) CPR is crucial to keep enough oxygen to the brain until more advanced life support can get to the victim. That advanced life support is mainly an AED.

Red Cross poster aed/cpr: photo of automated external defibrillator pads being applied

If CPR is started right away, 911 is contacted and an AED can get to the person quickly, they stand about a 60% to 70% chance of survival. (An answer to a test question in our class will be that for every one minute defibrillation is delayed, the victim loses 10% chance of survival.)

The statistics break down like this:

Up to 50% of victims in cardiac arrest will have ventricular fibrillation. The heart will have lots of electrical activity, but it will be disorganized. An AED will consider this a shockable rhythm.

In less than 10% of cases, the rhythm will be ventricular tachycardia. The electrical activity in the heart is organized, but so rapid that the heart's chambers can't fill with enough blood to pump properly. An AED will consider this a shockable rhythm.

In 15% to 20% of victims in cardiac arrest, the heart rhythm is pulseless electrical activity. The electrical rhythm is mostly normal, but the heart itself is sick. An AED will not detect any shockable rhythm.

In the rest of the 20% to even 50% of victims in cardiac arrest, the heart has stopped any electrical activity. People sometimes refer to this as flatline, since the usual wavy line on a ECG becomes flat. The name for this is asystole. It can be caused by a terminally sick heart, extreme blood loss, or ventricular fibrillation that went untreated. An AED will not detect any shockable rhythm.


(Remember, you do not need to know what kind of, or lack of, electrical activity is going on. Just follow what the AED says.)

Below, a true story from the National Park Service Morning Report of a rare instance of CPR alone working.

Bering Land Bridge National Preserve (AK)

Life Saved Through Rapid Response

Interpretive ranger Kaci Fullwood was closing up the park’s headquarters office at 5 p.m. on August 26th when she received a report of a man complaining of chest pain in the main lobby of the building, which is leased by several different agencies.

While administrative assistant Tracy Glaz called 911, Fullwood located the man and found him to be conscious and complaining that his chest hurt. Shortly thereafter, the 55-year-old man stopped breathing and his pulse failed. Fullwood and subsistence ranger Fred Tocktoo immediately began performing CPR. After two cycles of CPR, the man's pulse was restored and he started breathing on his own. Nome emergency services personnel arrived on scene a few minutes later and the patient was transferred to their care. [Submitted by Lindy Russell, Chief Ranger]


In June, 1999, Chicago's O'Hare Airport installed AEDs, located so that an AED was within one minute walking distance of anywhere in the airport. In the first ten months 14 cardiac arrests occurred and nine of the victims survived. That's a 64% survival rate, compared to 3% - 4% with CPR alone.

At the New England Journal of Medicine website, read an article on the results of casino AED use:

Casino AED use

AEDs aren't just for adults. Over 300 children die yearly from preventable sudden cardiac arrest (SCA) while playing sports.

 Updated Wednesday, September 21, 2005 at 12:55:31 PM by Mary Donahue -
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