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Harvard Commentaries
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Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


Medical Myths Medical Myths
 

CPR: Less Effective Than You Might Think


October 23, 2012

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center

Healthy Lifestyle
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Medical Myths
CPR: Less Effective Than You Might Think
CPR: Less Effective Than You Might Think
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You may have the impression from television shows or movies that CPR is a highly effective emergency treatment for anyone who has collapsed. It surprises many to learn that the dramatic CPR results they often see are a myth. In fact, CPR is rarely effective, and only in certain circumstances is its success rate anything other than dismal.
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Harvard Medical School Commentary
2014-10-23


Imagine your typical TV drama. A child, playing in the park, hovering too close to the pond, falls in. His parents, distracted for a few moments, soon notice that their child is missing. Frantic, they call her name and look everywhere, and it dawns on them. Perhaps she fell in. When they finally locate their daughter and pull her out, she is no longer breathing and has no signs of a pulse. Instinct would tell the viewer that someone would come to the rescue and use CPR to save the day. The child would sputter, wake up, and be returned, shaken but otherwise unharmed, to her parent's arms.

CPR (cardiopulmonary resuscitation) is a method of trying to restore circulation and breathing for a person who has no pulse or is not breathing. You may have the impression from television shows or movies that CPR is a highly effective emergency treatment for anyone who has collapsed.

It surprises many to learn that the dramatic CPR results they often see are a myth. Unfortunately, CPR is often ineffective, and only in certain circumstances is its success rate anything other than dismal. This is not to say it should be abandoned in dire situations, but in general, the expectations of loved ones or those performing CPR are often higher than the situation warrants.

CPR can and does work, but CPR lacks the magical quality people often associate with it. As I've said in other columns, medical myths often have some truth behind them: A drowning victim should promptly receive CPR, and good outcomes may follow as depicted in the typical TV drama. However, the success rate of CPR varies widely, based on many factors, including:

  • The cause of cardiac or respiratory arrest
  • The underlying health of the victim
  • The time elapsed between the arrest and CPR
  • The technique used by the person performing CPR

For example, when a person has stopped breathing because of low body temperature (such as someone rescued after falling through ice into a cold lake) or another readily reversible condition, the success rate is higher. On the other hand, when an elderly person has stopped breathing because of heart problems or pneumonia, especially when other medical problems are present, CPR has a very low success rate.

The value and limitations of CPR continue to evolve. This is reflected by published studies and changing guidelines. For example, studies in recent years suggest that for untrained bystanders receiving directions by emergency dispatchers, chest compressions alone may be as effective as compressions with artificial respiration (breathing into the person's mouth to provide oxygen). Guidelines released in November 2005, suggest more frequent and more rapid chest compressions for most people requiring CPR. The American Heart Association (AHA) announced in 2008 that rapid, deep chest compressions — at a rate of 100 per minute — work about as well as "standard CPR" (which includes mouth-to-mouth breathing) in adults until emergency medical personnel arrive. In addition, battery-powered defibrillators (that shock the victim's dangerously abnormal heart rhythm back to a safer, more stable rhythm) are becoming smaller, easier to use and increasingly available. These automated external defibrillators (AEDs) may increase the effectiveness of emergency rescues.

The most recent AHA guidelines were published in 2010 and emphasize chest compressions over mouth-to-mouth breathing. The compressions should be done first, applying 30 compressions prior to providing any breaths. Compressions should be "hard and fast," that is, provided at a rate of at least 100 per minute with a compression depth of at least 2 inches, stopping only to provide 2 breaths after every 30 compressions. For the untrained observer provider CPR, the new recommendations suggest hands-only technique (compressions only, no mouth-to-mouth breathing) until emergency personnel arrive.

As opposed to many medical myths, researchers have reliable data concerning the success rates of CPR (without the use of automatic defibrillators) in a variety of settings:

  • 2% to 30% effectiveness when administered outside of the hospital
  • 6% to 15% for hospitalized patients
  • Less than 5% for elderly victims with multiple medical problems

In June 1996, the New England Journal of Medicine published a study about the success rates of CPR as shown on the television medical shows "ER," "Chicago Hope" and "Rescue 911." According to the shows, CPR successfully revived the victim 75% of the time, more than double the most conservative real-life estimates. A more recent study published in 2009 suggested that the immediate success rate of CPR on television may be more realistic; however, discharge from the hospital and longer-term survival were rarely mentioned in TV dramas. In addition, while most CPR is actually performed on sick, older individuals with cardiac disease, most victims in television dramas are young and required CPR following trauma or a near-drowning — conditions with the highest success rates.

Finally, patients on TV shows usually die or fully recovered. In real life, many of those who are revived by CPR wind up severely debilitated. One reason may be that, as noted by a study published in the January 2005 issue of the Journal of the American Medical Association, CPR is frequently not administered adequately, even when provided by trained ambulance personnel. Improved technique (including more frequent and rapid compressions, as recommended in the new guidelines) and use of automatic defibrillators could dramatically improve success rates.

The low success rate of CPR may be an example of how a medical myth is perpetuated by the media because it is more appealing than the truth. Unfortunately, sugar-coating the concept of CPR leads to unrealistic expectations when a loved one requires CPR or is ill, and heroic measures are under consideration. A better understanding of when CPR may be effective and when it is highly unlikely to help will better serve everyone in the unfortunate event of catastrophic illness or injury. If you learn to administer CPR, you may save someone's life, so learning the proper technique is worth the effort. However, you should not expect the results you see on television.

Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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