When someone has a heart attack, seconds count.
A lot of people are reluctant to do mouth-to-mouth CPR on a total stranger.
Now, a group of Japanese researchers says you do not have to.
For years, experts have recommended chest compressions followed by two short breaths to revive someone who has had a heart attack.
Now there's evidence the breathing may do more harm than good. "If you breathe for me, you increase the interthorasic pressure and you decrease forward blood flow. So, not only is ventilation not helpful, it's harmful," says Dr. Gordon Ewy of the University of Arizona.
Japanese researchers found in four thousand real life situations.
People who received chest compressions only, no breathing, fared twice as well.
Even for those who had stopped breathing and received no ventilation twice as many were still alive a month later.
"They have plenty of oxygen in the blood already. You want to pump it around a bit," Dr. Stuart Seides of the Washington Hospital Center says.
Two years ago, the American Heart Association revised its guidelines to emphasize more chest compression, but they still recommend breathing, because CPR is used not only for cardiac arrest, but also the less common respiratory arrest, or things like drowning, choking, and drug overdoses where the body desperately needs oxygen.
Doctors say the public can be trained to quickly recognize the difference in cardiac and respiratory arrest so they will know which technique to use in an emergency.
In the US, more than a million people suffer heart attacks every year.
Half of them do not make it.
Half of those die in the first hour.
Experts say even a five minute delay can cause permanent damage, or death.
The key is to get help fast.