The old way took time and delayed the start of chest presses, which keep the blood circulating to the heart and brain.
The new advice, which was released by the /*American Heart Association*/, ditches the old "ABC" training of airway-breathing-compressions that called for rescuers to give two breaths first, then alternate with 30 presses.
"The feeling was that if you start with chest compressions more people would get some support after a sudden cardiac event," said ABC News' senior health and medical editor Dr. Richard Besser.
Dr. Besser says compressions make the best use of what oxygen is available.
"Initial minutes after a cardiac arrest there is still oxygen in your blood," said Dr. Besser. "So the sooner you start your blood circulating to your brain, the greater your chance of survival."
With the revised guideline, the 30 chest presses come first and then the two breaths follow. The guideline also advises to push deeper, at least 2 inches in adults and that rescuers should pump the chest of the victim at a rate of at least 100 compressions a minute.
The change applies to adults and children, but not newborns.
The Associated Press contributed to this report.
