You're at a family gathering or a crowded shopping mall when, suddenly, someone drops to the floor with a heart attack, unable to breathe.

How do you respond? Your first instinct might be to provide mouth-to-mouth resuscitation, but that that might not be necessary. A new study published in the Journal of the American Medical Association (JAMA) says Chest compression-only bystander CPR may be as effective as conventional CPR with rescue breathing for out-of-hospital cardiac arrest.

Out-of-hospital cardiac arrest is a major public health problem, affecting approximately 300 000 people in the U.S. each year. Although survival rates vary considerably, overall survival is generally less than 10 percent among those in whom resuscitation is attempted.

Having a bystander respond with CPR significantly increases a victim's chances of survival, but unfortunately, bystanders respond in fewer than 30 percent of cases.

Few responders

Why so few people responding? Researches guessed that the expectation that mouth-to-mouth breathing assistance was needed proved to be intimidating. Bystanders were either reluctant to make such intimate contact with a stranger, or felt they lacked the knowledge of how to do it correctly.

When researchers analyzed more than 4,000 cases of out-of-hospital cardiac arrest, they found that victims who received compression-only resuscitation did just as well as those who received traditional mouth-to-mouth assistance. In fact, their survival odds were a little better.

Among patients with out-of-hospital cardiac arrest, layperson compression-only CPR was associated with increased survival compared with conventional CPR, leading to a recommendation for bystanders to administer chest-only CPR when confronted with such an emergency.

Policy change might lead more people to respond

"In this study, we evaluated whether intentional, widespread public endorsement of compression-only CPR for adult sudden cardiac arrest would be associated with an increased likelihood that lay rescuers would perform CPR and an increased likelihood of survival to hospital discharge compared with no bystander CPR and conventional CPR," the authors concluded.

The Red Cross has, for some time, encouraged untrained laypersons to respond in emergency situations with compression-only CPR.

"We recognize that upon witnessing the sudden collapse of an adult, calling 9-1-1, and providing Compression-Only CPR until an AED is available is an acceptable alternative for those who are unwilling, unable, or not trained to perform full CPR," the Red Cross said.

The video below, produced in conjunction with the Red Cross, shows how to administer compression-only CPR.