One of the new studies, carried out in London and the Seattle area, involved more than 1,900 people who witnessed someone in cardiac arrest and called 911 or some other emergency number. Emergency dispatchers instructed callers to do either hands-only CPR or an older form of standard CPR that alternates 15 pushes with two quick breaths.
The second study was done in Sweden and included nearly 1,300 people.
In both studies, there was no significant difference in the survival rates of people who got conventional CPR and those who got the hands-only version.
The studies are being published in Thursday's New England Journal of Medicine.
While there is no good national data on how often hands-only CPR is used, Dr. Ben Bobrow, who directs the Arizona Department of Health Services' emergency medical system, believes it is catching on.
"We've seen a huge trend in hands-only CPR in Arizona and I believe that trend is spreading across the country. I think these findings will further promote that," he said.
Many people think of traditional CPR as difficult, and to some extent it is. The victim's head has to be tilted back, the airway cleared, the nose pinched and the mouth completely covered with the rescuer's. A lot of people have trouble with it, said Don Pederson, a dispatcher in Seattle's King County, who participated in the U.S. study.
"A lot of the times they weren't getting air in there correctly," with oxygen escaping out the sides of the mouth, Pederson said.
Rea and his colleagues believe some bystanders perform mouth-to-mouth so poorly that the interruption reduces blood flow.
Worry about doing CPR correctly was the No. 2 reason many people don't attempt it, according to a Michigan study published in 2006. The No. 1 reason? People are too panicked.
The "ick" factor of putting lips to a stranger's mouth - and picking up the stranger's germs - was cited by only a tiny fraction of people in the study. However, it may be a more significant issue than the study showed, at least in some communities, experts say.
Traditional CPR is still the preferred form of resuscitation for children or adults who have stopped breathing because of choking, drowning or other respiratory problems.
New England Journal:
The Associated Press