For years, anyone learning CPR, emergency resuscitation, was taught the “ABC”: Check the airway for blockages, give breaths, then circulate the blood. New guidelines issued recently by the American Heart Association turn that alphabet on its head, punctuating a shift that has led emergency responders to emphasize compression of the chest over all else when treating victims of cardiac arrest. The new catch-phrase is “C-A-B”, as in start pushing on the chest before doing anything else. The science behind the changes is simple. In an adult who has been breathing normally, for several minutes even after cardiac arrest there is enough oxygen in the bloodstream to maintain the heart and brain, as long as compressions circulate that oxygen. In this scenario, pausing to provide oxygen through rescue breaths is not only unnecessary, but harmful because it requires the rescuer to stop pressing on the chest for at least several seconds. Dr. Gordon Ewy of the Sarver Heart Center at the University of Arizona, who led some of the first animal studies on CCR, says rescue breaths can also be harmful because they cause lower air pressure in the chest cavity, which slows down circulation, the most important element in the whole process. The new guidelines also call for faster and more forceful compressions than in the past. The new standard is to compress the chest at least two inches on each push, at a rate of 100 compressions per minute. The AHA says the perfect pace is that of the Bee Gees’ hit “Staying Alive”. The AHA guidelines also uphold a 2008 recommendation that untrained responders call 911 but then forget rescue breathing completely, and simply press on the victim’s chest until help arrives. Going a step beyond that, the 2010 guidelines “strongly recommend” that 911 dispatchers guide callers in “compression-only” CPR, sometimes known as CCR. However, medical professionals and trained lay people are still urged to give the victim two “rescue breaths” in between each series of 30 chest compressions. All the changes apply only to adult victims who collapse of cardiac arrest; artificial respiration is still recommended for children and for adults in a few cases, including near-drowning and drug overdose. Additional research in recent months has added to the evidence that chest compressions are the key to effective resuscitation. One clear benefit of eliminating mouth-to-mouth is that by eliminating fear of infections, you get more people to jump in. Since 2004, the number of bystanders who attempt CPR has gone from 28 percent to 40 percent. Dr. Michael Sayre, an emergency physician at the Ohio State University and a spokesman for the AHA, says the odds of survival roughly double if a bystander steps in to provide CPR. According to Sayre, if the national rate of bystander assistance could be raised to 70 percent, the same rate as the city of Seattle, where a public education campaign has run for decades, a minimum of 20,000 lives would be saved every year.