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The mantra for CPR has become ‘push fast and push hard’ – at a rate of 100 times a minute.J.P. MOCZULSKI/The Globe and Mail

Hands-only CPR may not be ideal for saving people who have suffered cardiac arrest in a remote area, or if it takes a long time for an ambulance to arrive, a new study warns.

The guidelines for CPR, or cardiopulmonary resuscitation, were revised three years ago to encourage more bystanders to perform the potentially life-saving procedure. Traditional CPR calls for a combination of chest compressions and quick breaths into the mouth. But many people are reluctant to do mouth-to-mouth on a stranger.

The medical experts who drafted the revised guidelines concluded that doing something was better than nothing, so people were urged to perform rapid chest compression to keep the blood circulating until professional help arrived.

The mantra for CPR has become "push fast and push hard" – at a rate of 100 times a minute. "That's about the tempo of the song Stayin' Alive by the Bee Gees," one of the authors of the international guidelines was quoted as saying.

However, a new study challenges the broad application of the recommendations.

"The authors of the guidelines clearly weren't thinking about people in rural or remote communities or anybody in an urban area who might have to wait a long time for ambulance service," said Dr. Aaron Orkin, who is part of Rescu, a resuscitation-research team at St. Michael's Hospital in Toronto.

He's concerned that, without additional breaths, the oxygen in the bloodstream will become depleted long before paramedics arrive.

For his study, Orkin reviewed the 10 research papers that served as the foundations for the hands-only guidelines. The studies found there is often enough oxygen in the bloodstream to sustain life if chest compressions are started right away. But of these 10 papers, only one included rural populations and people who had to wait longer than 15 minutes for an ambulance.

"One of the interesting features of those studies is that they had extremely fast response times," said Orkin, who is also an assistant professor in the division of clinical sciences with the Northern Ontario School of Medicine.

Urban-based studies can't always be applied outside of big cities, he said. "The existing data is not adequate to provide robust conclusions regarding compression-only bystander CPR in settings with prolonged EMS [emergency medical service] response times," he writes in his study, published in the Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine.

He suggests the "push hard, push fast" advice would be better stated as "push hard, push fast, if you're downtown."

So how long should you wait before giving a breath to a patient stricken by cardiac arrest? Orkin says there isn't enough evidence to answer that question. "There are gaps in what we know," he said. "We know that eventually people need breath, but no one is doing a study to find out where that line is. So we might not be giving people the best chance of survival."

Orkin hopes his study will prompt more research and lead to nuanced recommendations that recognize not everyone is in the same situation. "We need guidelines that are really designed to serve everybody, not just people who are in the downtown, have access to fast paramedic services, or live near big hospitals."

The Heart and Stroke Foundation, one of the key groups that promotes hands-only CPR in Canada, agrees that additional research is needed in rural communities. "We would clearly benefit from more studies there," said Andrew Lotto, manager of resuscitation for the foundation's Ontario branch. But he added the existing recommendations are "based on the best evidence we have."

Lotto noted the overall guidelines still state that CPR-trained individuals, and those who feel comfortable doing it, should attempt to provide ventilation during a rescue effort.

But the reality is that many people shy away from mouth-to-mouth, he said. "Our population-base engagement, at this point, is get involved – doing something is better than doing nothing."