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CPR: Less Effective Than You Might Think

By Rob Shmerling
Content provided by the Faculty of the Harvard Medical School

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.

There are new developments in CPR, including a study showing 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). New guidelines, released in November 2005, suggest more frequent and more rapid chest compressions for most people requiring CPR. While new guidelines are due in 2010, the American Heart Association 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.

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.

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