Two new studies report that when it comes to saving a life using cardiopulmonary respiration (CPR), the would-be lifesaver can drop the mouth-to-mouth and concentrate only on chest compressions. Knowing this may make bystanders more likely to jump in when someone is having a heart attack in public.

The first study, led by Thomas D. Rea at the University of Washington, randomly assigned emergency dispatchers to instruct 911 callers to administer chest compressions only or chest compressions and mouth-to-mouth to a person having a heart attack. In total, 1941 patients were included in the study. Rae and his team compared the survival rates of the two groups of patients at the time of hospital discharge. They found that for patients who received only chest compressions their survival rate was 12.5%, and for those who received both parts of CPR, the survival rate was 11%, which was not a statistically significant difference.

The second study, led by Leif Svensson at the Karolinska Institutet in Sweden, had a similar approach but survival was tracked over 30 days after the patient's heart attack. A total of 1,276 patients were included in the study, also randomly assigned to receive chest compressions only or classic CPR. At the 30 day mark, 8.7% of the patients receiving only chest compressions survived, vs. 7.0% of those receiving both components of CPR.

This is good news for bystanders, who may be scared to jump in when a stranger or even a loved one collapses. Both studies show that if you are in the presence of someone who appears to be having a heart attack, it's at least as effective to do chest compressions only, compared to the standard two-part CPR.

It always a good idea to call 911 before administering chest compressions, so that a trained dispatcher can walk you through it. More information on how to administer chest compressions can be found at the American Heart Association's Hands-Only™ website: http://handsonlycpr.org/. And as the American Heart Association says: "Don't be afraid. Your actions can only help."

Both studies were published in the July 19, 2010 issue of The New England Journal of Medicine.