CHICAGO - Hands-only CPR doesn't just eliminate the "yuck factor." A new study shows it can save more lives.

It's the first large American study to show more adults survived cardiac arrest when a bystander gave them continuous chest presses to simulate a heartbeat, compared to traditional CPR with mouth-to-mouth breathing.

"Anyone who can put one hand on top of the other, lock their elbows and push hard and fast can do this. No risk, no fear of causing harm," said lead author Dr. Ben Bobrow of the Arizona Department of Health Services in Phoenix.

"We want to take away all the reasons bystanders do nothing when they witness another person collapse."

With hands-only CPR, advocates say, potential rescuers don't have to contemplate what for some could be the "yuck factor" of putting their mouth to an unconscious person's mouth and breathing for them.

For others, the trimmed-down method simplifies a confusing procedure learned years ago and barely remembered - How many breaths? How many chest compressions? Are you supposed to pinch the nose?

Standard CPR with mouth-to-mouth and chest compressions is still best for very small children and victims of near-drowning and drug overdose, experts say, instances where breathing problems probably led to the cardiac arrest.

Nonstop chest compressions work better for adult cardiac arrest because most people take too long to do mouth-to-mouth, said senior author Dr. Gordon Ewy (pronounced AY'-vee) of the University of Arizona Sarver Heart Center.

After cardiac arrest, oxygenated blood can't get to the brain without help. Most rescuers take about 16 seconds to perform two CPR breaths - long enough to starve the organs of oxygen.

"Your hands are their heart," Ewy said. "When you stop pressing on the chest, blood flow to the brain stops."

A 2007 study of 4,068 out-of-hospital cardiac arrests in Japan found similar results, but other studies have found no difference between the two CPR methods.

The study, which appears in Wednesday's Journal of the American Medical Association, is also the first to show a statewide awareness campaign can increase bystanders' willingness to try CPR.

Arizona reached 500,000 people through public service announcements, YouTube, free classes, e-mails and inserts in utility bills, all promoting hands-only CPR.

Researchers looked at 4,415 adult cardiac arrests outside of hospitals in Arizona from 2005 to 2009 during the campaign.

The rate of bystanders attempting any type of CPR increased from 28 percent in 2005 to 40 percent in 2009. Bystanders were more likely to use hands-only CPR over traditional CPR as time went on.

And victims who got hands-only were more likely to survive: 113 of 849 victims (13 percent) who received the hands-only method survived, compared to 52 of 666 victims (about 8 percent) who received conventional CPR.

Greg Stewart, a 54-year-old father of five, is one of the survivors thanks to hands-only CPR. His heart stopped at his Scottsdale, Ariz., home as he and his wife, Lu Ann, sat down to watch "Survivor" on television last year. She called 911.

"The dispatcher told me what to do. I got him out of the chair and onto the floor and at that point his face was really, really dark," Lu Ann Stewart said. She fought down panic.

With her daughter taking over the 911 call, Lu Ann began pressing her husband's chest.

"I got up on my knees and just started pressing as hard as I could. By golly, his color started to lighten," she said. She kept pushing hard and fast, ignoring her tired muscles. "He was gone a long time. I kept the blood pumping."

Minutes later - "it felt like hours" - paramedics arrived and took over.

Today, Greg Stewart is grateful.

"She's not a big lady," he said of his wife, his childhood sweetheart. "And yet she kept going and kept going."

His cardiac arrest was the result of a heart attack from blocked arteries; he later had bypass surgery.

The steps:

• If someone collapses, doesn't respond to gentle shaking and stops normal breathing, call 911 or tell someone else to call.

• With the victim on his back, place the heel of one of your hands atop the other on the middle of the victim's breastbone.

• Lock your elbows. With your shoulders over your hands, fall forward using your body weight. Press 100 times a minute. Think of the Bee Gees song "Stayin' Alive" for the tempo.

• If an automated external defibrillator is available, switch it on and follow the instructions.

• If not, continue chest compressions until paramedics arrive.

In 2008, the American Heart Association said hands-only CPR works just as well as standard CPR for sudden cardiac arrest in adults. Later this month, the association plans to announce new CPR guidelines and is keeping them under wraps until then.

Guidelines committee chair Dr. Michael Sayre said the Arizona findings are too new to have been considered.

"Certainly their findings are compelling," Sayre said.

Sayre said he's impressed by the increase in bystander CPR achieved in Arizona.

"The real problem we have isn't the small difference between methods of CPR," he said. "The real problem we have is people doing nothing."