Technology & Science

Cause of avalanche death for Canadian victims differs from Europeans: study

Suffocating in snow is commonly thought to be the main cause of death from avalanches, but researchers say traumatic injuries also need to be considered for many of the accidents in Western Canada.

Suffocating in snow is commonly thought to be the main cause of death from avalanches, but researchers say traumatic injuries also need to be considered for many of the accidents in Western Canada.

"With an overall perspective, our findings indicate that one-third of victims have already suffered potentially lethal trauma before the avalanche comes to a stop, and most of those will die primarily of their injuries," said Dr. Jeff Boyd of the Banff Mineral Springs Hospital, an emergency room doctor and mountain guide who led the study in Thursday's online issue of the Canadian Medical Association Journal.

"And, most of them won't be completely buried."

European studies have reported that asphyxia or severe lack of oxygen from suffocating under the snow was responsible for most deaths, and major trauma caused five per cent.

But Boyd and his colleagues reported that trauma alone caused 48 or 24 per cent of 204 avalanche deaths in British Columbia and Alberta from 1984 to 2005.

The rate of death from trauma ranged from nine per cent for snowmobilers to 42 per cent for ice climbers.

Also, 13 per cent of the asphyxia victims who had autopsies had major trauma based on injury severity scores.

Graced with snow in trees

"Our findings should guide recommendations for safety devices, safety measures and resuscitation," the study's authors concluded.

For example, spinal precautions should be observed. Then trauma measures from combat medicine such as decompression of a collapsed lung with tension could be applied, Boyd said.

Since the majority of trauma victims hit trees, the researchers suspect that terrain preference is a main contributing factor.

"We are graced with excellent snow in the trees," Boyd said. "Backcountry, helicat and out-of-bounds skiers and snowboarders spend a considerable proportion of their time in forested terrain."

In comparison, Europeans have less access to forested areas, and the snow quality may be poorer, he added. Snowmobilers also prefer open slopes.

Early rescues credited

"Young skiers and snowboarders were over-represented in our series," the researchers wrote. "The Canadian Avalanche Centre should continue to focus on education of this high-risk group, and social science research is essential to determine effective education strategies."

The higher rate of death by trauma in the Canadian avalanches, especially in helicopter and snowcat accidents, could be partly explained by early rescue that saves avalanche victims from suffocating, Dr. Hermann Brugger from Innsbruck Medical University in Austria said in a commentary accompanying the study.

"It is possible that the high rate of trauma mortality in the current study was because of an exceptionally high rate of rescue within a short period after avalanche burial when asphyxia has had less chance to occur," Brugger wrote.

Helicopter skiers carry avalanche transceivers and are accompanied by trained guides who may be able to extricate people quickly in case of burial.

How long someone is buried is important, Brugger said, because the probability of survival decreases from 91 per cent after 18 minutes of burial to 34 per cent after 35 minutes.

"Boyd and colleagues conclusively show that the on-site management of care for avalanche victims needs to be revised so that trauma management is given more prominence," Brugger concluded.

March is statistically the month with the greatest number of fatalities, and unusual early snow conditions this winter have caused more than the annual average of deaths.

British Columbia and Alberta account for 88 per cent of avalanche deaths in Canada, according to the researchers.