To do that, some 380 international scientists analyzed 20,000 or more studies and came up with several recommendations.



Overall, the guidelines -- which urge laypeople to take a CPR course -- emphasize a "back-to-basics" approach.

"The most common reason people die is because no one nearby knew CPR or didn't actually do it after cardiac arrest happened," said Dr. Michael Sayre, volunteer chairman of the American Heart Association's basic life support subcommittee, and associate professor of emergency medicine at Ohio State University.

"One of the reasons for that is the skill has been very complicated," he added. "We believe that the first step towards bystanders taking action is to improve the accessibility and quality of CPR training and to simplify instructions."

The biggest change is in the ratio of chest compressions to breaths, which under the new guidelines is now 30 compressions for every two breaths, compared to 15 compressions for every two rescue breaths in the 2000 guidelines.

"The more times someone pushes on the chest, the better off the patient is, the more blood flows to the heart and brain and other vital organs," Sayre explained.

This 30-to-two ratio should be used for everyone. This makes it less confusing for layperson's to remember the important numbers.

The rate of compressions (100 per minute) has not changed. The new guidelines do, however, eliminate some steps, including checking a victim's pulse if it has already been ascertained that he or she isn't moving and breathing. This is based on the fact that some people may not be able to find a pulse or find a very weak pulse and do not start cpr.

Another change is the timing of heart rhythm analysis and CPR when using automatic external defibrillators (AEDs). Before, an AED analyzed the rhythm before and after delivering a shock and the whole sequence could be repeated as many as three times before CPR was begun, thus losing precious time.

Now, the guidelines recommend one shock followed by two minutes of CPR before going back to an AED. This one shock has been shown to return the heart back to a normal rhythm about 90% of the time if used within the first 2-3 minutes the person has heart trouble.