A National Institutes of Health study of public access defibrillation -- the most extensive clinical trial of its kind -- shows that people with no other medical training can save lives by helping cardiac arrest victims before emergency medical services arrive.

While the results are not surprising to many who have implemented these programs in such places as casinos and airports, they have been anticipated by experts seeking hard evidence.

"We knew we could save more lives if we could get to people sooner, and we knew we could get there sooner if the defibrillator was on site and people knew how to use it," says Jerry Potts of the American Heart Association. "What we didn't have until now was a randomized study that proved it." The results were presented at the AHA's annual scientific meeting here.

In the study, nearly 20,000 people were trained to use defibrillators, computerized devices that even children can use to restart a heart. Volunteers were located in 993 public places in 24 areas of the United States and Canada.

The sites were equally divided into those that had access to a defibrillator and those that did not, requiring volunteers there to use cardiopulmonary resuscitation. During the 21/2-month study, there were 232 cases of cardiac arrest and 44 survivors. Of the survivors, 29 had been treated with a defibrillator, 15 with CPR.

CPR is vital to cardiac arrest survival, but when a heart is quivering in ventricular fibrillation, only a shock from a defibrillator will save the life, experts say.