Doctors, nurses and paramedics often fail to perform CPR correctly to restart stopped hearts, two new studies suggest.

Outdated training may be part of the problem in following the strict guidelines for cardiopulmonary resuscitation, a first aid procedure for an unconscious person whose breathing and/or pulse have stopped.

The technique buys time, protecting the heart and brain until the heart can pump in a normal rhythm, usually after shocking.

Early CPR and defibrillation within eight minutes improve survival.
Early CPR and defibrillation within eight minutes improve survival.

Common problems faced by rescuers include:
  • Not pushing hard enough.
  • Failing to push frequently enough (100 to 120 compressions per minute is recommended).
  • Breathing air into the lungs too often.

In the studies, rescuers used an experimental sensor that assesses the quality of CPR, such as the depth of chest compressions.

The company that developed the device funded the research, which appears in Wednesday's Journal of the American Medical Association.

"You can't fix what you can't measure," said Dr. Lance Becker, a professor of emergency medicine and director of resuscitation at the University of Chicago. "Performing CPR was like driving a car without a speedometer, based more on feel than on feedback."

Researchers didn't expect rescuers to perform skills they learned in the classroom perfectly, given they were tested in the stress-filled chaotic environment of real-life cardiac arrests.

Lars Wik of Ulleval University Hospital in Oslo found paramedics and caregivers failed to start CPR quickly enough in nearly half the 176 cases of heart attacks in Stockholm, Sweden; Akershus, Norway; and London.

Sixty-one of the patients, or 35 per cent, had their heartbeats restarted and circulation resumed to avoid brain damage. The remaining 65 per cent could not be revived and they died.

In the other study of 67 adult patients at the University of Chicago, doctors and nurses failed to folllow at least one CPR guideline 80 per cent of the time. Twenty-seven of the patients were revived.

Becker, who co-authored the U.S. study, said the device used in the studies offers a reliable way to assess CPR and improve survival rates, although the studies were too small to assess if it helped.

The device is approved for experimental use in the U.S., and the manufacturer is seeking permission from the Food and Drug Administration to sell it commercially.