New guidelines switch the steps for cardiopulmonary resuscitation (CPR), telling rescuers to start with hard, fast chest presses before giving mouth-to-mouth.

The change puts “the simplest step first" for traditional CPR, says Michael Sayre, co-author of the guidelines issued by the American Heart Association on Monday.

In recent years, CPR guidance has been revised to put more emphasis on chest pushes for sudden cardiac arrest. In 2008, the heart group said untrained bystanders or those unwilling to do rescue breaths could do hands-only CPR until paramedics arrive or a defibrillator is used to restore a normal heart beat.

Lifesaver: The change ditches the old ABC training.

The change ditches the old ABC training—airway-breathing-compressions. That called for rescuers to give two breaths first, then alternate with 30 presses.

Dr Sayre says that approach took time and delayed chest presses, which keep the blood circulating. “When the rescuer pushes hard and fast on the victim’s chest, they’re really acting like an artificial heart. That blood carries oxygen that helps keep the organs alive till help arrives," says Dr Sayre, an emergency doctor at the Ohio State University Medical Center, US.

“Put one hand on top of the other and push really hard," he says.

Sudden cardiac arrest—when the heart suddenly stops beating—can occur after a heart attack or as a result of electrocution or near-drowning. The person collapses, stops breathing normally and is unresponsive. Survival rates from cardiac arrest outside the hospital vary across the country—from 3-15%, says Dr Sayre.

Under the revised guidelines, rescuers using traditional CPR should start chest compressions immediately—30 chest presses, then two breaths. The change applies to adults and children, but not newborns.

One CPR researcher, though, expressed disappointment with the new guidelines. Gordon Ewy of the University of Arizona Sarver Heart Center thinks everyone should be doing hands-only CPR for sudden cardiac arrest, and skipping mouth-to-mouth. He says the guidelines could note cases where breaths should still be given, such as near-drownings and drug overdoses, when breathing problems likely led to the cardiac arrest.

Ewy is one of the authors of a recently published US study that showed more people survived cardiac arrest when a bystander gave them hands-only CPR, compared with CPR with breaths.

The guidelines issued also say that rescuers should be pushing deeper, at least 2 inches in adults. Rescuers should pump the chest of the victim at a rate of at least 100 compressions a minute—some say a good guide is the beat of the old disco song Stayin’ Alive.

Ahamed Idris, of the University of Texas Southwestern in Dallas, says people are sometimes afraid that they’ll hurt the patient. Others have a hard time judging how hard they are pressing, he says.

“We want to make sure people understand they’re not going to hurt the person they’re doing CPR on by pressing as hard as they can," he says.

Idris, who directs the Dallas-Fort Worth Center for Resuscitation Research, says that for the last two years they’ve been advising local paramedics to start with chest compressions and keep them up with minimal interruptions. That, along with intensive training, has helped improve survival rates, he says.

He says they found paramedics hadn’t been starting compressions until the patient was in the ambulance and lost time getting airway equipment together.

“The best chance was to start chest compressions in the house, immediately," he says.