Curie high school students Sherrell Christian, left, and Lucero Contreras listen to Eileen Ryan, Assistant Risk Manager for the Chicago Public Schools describe how to use a defibrillator during a CPR and defibrillator training session in Chicago, Friday, Feb. 28, 2003. (AP Photo/Aynsley Floyd)

Using a mobile app to find and alert people with CPR training who are near someone having a cardiac arrest improves the chances of the victim getting CPR and the person's survival rate, according to studies published in the New England Journal of Medicine last week.

The chances of surviving a cardiac arrest outside a hospital are dismally low, according to past research and the NEJM studies. In the studies conducted in Sweden, which looked at out-of-hospital cardiac arrests from Jan. 1, 1990 through Dec. 31, 2011, only 4 percent of the victims survived more than 30 days after the incident — if they didn't have someone performing CPR or using a defibrillator before emergency responders got to the scene.

But the survival rate more than doubled -- to 10.5 percent -- if a bystander performed cardiopulmonary resuscitation, the studies found.

The researchers then investigated if bystander-initiated CPR rates could be increased with the use of mobile technology.

A mobile "on-call" system with GPS was used to find and alert anyone with CPR training who was near, about 1,600 feet from, someone having a cardiac incident. The app pulled information from 911 dispatchers and sent it to trained volunteers in the form of texts and automated calls. Researchers found that the technology significantly increased the rate at which bystanders initiated CPR.

In cases when the app wasn't used, only 48 percent of cardiac arrest victims got CPR from bystanders, the study found. But when the on-call system was activated, that rate jumped to 62 percent.

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"We want to spread this — make it bigger and larger," said Jacob Hollenberg, one of the authors of the study and an associate professor at Karolinska Institutet. "We're looking for international cooperation if possible. We think this is universal."

Similar technology is gaining ground in the United States. PulsePoint, a nonprofit based in the San Francisco area, already works with emergency dispatchers in more than 1,300 communities and 22 states, with about 300,000 trained volunteers.

Still, the system has its challenges. PulsePoint only sends its "citizen respondents" to incidents that occur in public places, not in homes or private places. Shannon Smith, a spokeswoman for the organization, said the policy was put into place to protect volunteers and PulsePoint from liability, limiting the app's reach to about 20 percent of cardiac arrest cases.

"There are concerns around privacy and the public's willingness to knock on the door (to do CPR)," said Michael Sayre, a professor at the University of Washington who will be using PulsePoint later in the summer to study how it's impacting cardiac arrest incidents in Seattle.

Sayre's study, similar to the one done in Stockholm, will focus on knowing what portion of the population needs to be trained in CPR to respond to all cases.

The Stockholm study collected about 10,000 volunteers, or about 1 percent of the city's total population, but other cities, Sayre suggested, may have different demands based on demographics. Poorer parts of cities may have more difficulty recruiting volunteers than others.

The mobile technology complements a big push over the past few years by groups like the American Heart Association and the American Red Cross to make CPR more accessible, especially by making training easier for ordinary people. Many groups administering the training have eliminated mouth-to-mouth resuscitation because it is difficult to do, and studies have found it isn't as important as compression.

Now, people just need to push down hard on the victim's chest. The pace should be 100 chest compressions per minute — pretty close to the beat of the Bee Gees's disco hit, "Stayin' Alive."

CPR is essentially manually pumping the heart, which is important in cases of cardiac arrest, which occurs when the heart malfunctions and suddenly stops beating. That's different from a heart attack, which is a blockage in the heart.

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Cardiac arrest can be the result of a heart attack, but it can also occur when the heart stops beating regularly — called arrhythmia — or due to a severe lack of oxygen.

Defibrillators can be used to get the heart back on its regular rhythm by delivering an electric shock throughout the body. Training groups have put an increased pressure on teaching people to use the devices. The mobile apps have features designed to locate automated external defibrillators near cardiac arrest incidents.

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