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Dispatches: Avalanche survival rates differ in Canada

Industry statistics based on Swiss curve proven less applicable in Coast Mountain conditions
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It's a thought that drives backcountry users to habitually reassess their strategy during every minute spent in the cold, pristine wilds of the Coastal Range. Avalanches are common enough to the steep pitches of B.C.'s terrain, easily wiping vast wilderness expanses clean of trees, rocks and whoever might stand in the way.

A terrifying force with little forgiveness, a snow slide is the top priority on any backcountry expert's mind, even when enjoying the deep, unfettered slopes that draw them there.

It's certainly what has dominated Simon Fraser University researcher Pascal Haegeli's thought process over the past decade.

An avid backcountry skier who did his PhD at UBC under famed avalanche expert Dave McClung, Haegeli is behind a study recently published in the Canadian Medical Association Journal that compares avalanche victims in Canada and Switzerland.

"The motivation of the study was that current avalanche rescue resuscitation guidelines are based on an avalanche survival curve that is only based on Swiss avalanche data," he said during a phone interview from Switzerland.

"We wanted to know whether that curve, and therefore the guidelines, are universally applicable and if not, then if the Canadian patterns are different, then we wanted to know more about the Canadian patterns so that rescue guidelines here can actually be adjusted to more specifically target the issues we have in Canada."

The avalanche survival curve displays a person's chance of surviving a complete burial as a function of time, essentially tying one's chance of survival to duration of burial. Data collected during Haegeli's studies included 301 Canadian and 946 Swiss subjects who had been completely buried in an avalanche. The information pointed to an unsettling conclusion based on three factors - trauma, asphyxia and proximity to trained medical care.

"What we found is that your chance of surviving a burial in Canada is lower at all times than in Switzerland," said Haegeli.

"For burials that are shorter than 10 minutes, in Canada there is a significantly higher rate of trauma than in Europe. We spend a lot more time in the trees while in Europe basically all back country activity is in the alpine."

Around a quarter of all avalanche deaths in B.C. occur from trauma sustained from hitting trees, going over cliffs and the pure violence of the slide itself. Only five to six per cent of European avalanche deaths relate to similar trauma.

Heavy snow conditions due to warmer temperatures in the coastal regions are more likely to contribute to asphyxia than the colder snow of the Rockies, which is comparable to Swiss conditions.

"We saw that asphyxia or the onset of asphyxia seems to be a function of snow climate," continued Haegeli. "In the maritime snow climates off the coast mountains it seems that asphyxia starts a lot earlier than in the Rocky Mountains where you have colder snow, it's blockier, in the coast mountains you basically get buried in a block of concrete."

International guidelines based on the Swiss data showed you had a reasonable chance to dig someone up alive within about 18 minutes of being buried with the survival chances in the first eight minutes hovering about 80 per cent. Based on Haegeli's Canadian data set a new recommended time period of 10 minutes was established - about half of what the guideline was before.

"An interesting side outcome of the study is that Canadians seem to dig up their companions a lot faster than the Swiss," said Haegeli.

"The average burial time in the Canadian data set was 18 minutes while in the Swiss it was 35.

"We don't have background data to explain that difference but I think one possible reason could be that in Canada we're simply aware that when you're in the back country you're on your own, you are really your buddy's only chance. So companion rescue has been a strong focus of Canadian avalanche training and it's paying off. Unfortunately it seems we have to do even better to get people out quickly."

The third factor in avalanche survival rates related to medical attention at the scene of the emergency and travel times to the closest medical care centre. The study revealed that the survival chance in prolonged burials - longer than 35 minutes - is significantly lower in Canada.

"I think it has something to do with the generally limited medical support at the accident site and during transportation to an advanced medical facility," said Haegeli. "I think we're somewhat limited by our geography, where in Europe you generally have a helicopter on site within 15 to 20 minutes, there's generally an emergency physician coming on site with that helicopter and you're back at a hospital fairly quickly. In comparison to Canada where that generally involves a lengthier flight to either Vancouver, Kamloops or Calgary."

Given the limitations of B.C.'s geography, Haegeli said rescue workers and backcountry users do a good job of handling avalanche scenarios, but advises search and rescue teams to increase training to get people out of dangerous situations.

For more information on avalanche safety and up to date conditions go to www.avalanche.ca .