Health

Canadian, Swiss avalanche survival rates similar

Survival rates for people buried in avalanches in Canada and Switzerland were almost the same over a 25-year period, but there were notable differences in fatality numbers, a new study has found.

Victims dug up faster in Canada

A sign in B.C.'s Glacier National Park tells visitors a trail is closed. Canadian data indicates a lower chance of survival at all burial durations compared to the Swiss survival model, but the poor survival curves for Canada were offset significantly because of faster extrication times. (Adrian Wyld/Canadian Press)

Survival rates for people buried in avalanches in Canada and Switzerland were almost the same over a 25-year period examined in new research, but there were notable differences in fatality numbers.

Data from 1980 to 2005 was extracted from the Canadian Avalanche Centre and the Swiss Federal Institute for Snow and Avalanche Research for the study, published Monday in the Canadian Medical Association Journal.

A total of 301 people who were completely buried in avalanches were in the Canadian database, with 946 in the Swiss database. The survival rates in the two countries were 46 per cent and 47 per cent, respectively.

According to the study, the Canadian data showed a lower chance of survival at all burial durations compared to the Swiss survival model.

However, the poor survival curves for Canada were offset significantly because of faster extrication times, the authors said.

Canada's avalanche victims spend less time buried

The median duration for burial in Canada was 18 minutes, compared to 35 minutes in the Swiss sample.

Compared to the Swiss survival curve — recording the probability of survival against the duration of burial — the Canadian curve showed a quicker drop at the early stages of burial and poorer survival associated with prolonged burial, writes Dr. Pascal Haegeli of Simon Fraser University in Burnaby, B.C., one of the authors.

Chances of survival for Canadians dropped earlier in the curve for a number of reasons.

There is a greater chance of trauma-related fatalities in Canada, greatly affecting the victim in the first 10 minutes after an avalanche occurs.

Also, Canadian avalanche terrain has more areas of denser snow, cutting the flow of oxygen to someone who has been buried, increasing the chances that person will die more quickly of asphyxiation.

After prolonged burials, typically meaning a person has spent up to 35 minutes in the snow before rescue, the Swiss survival rate is higher, largely because rescuers in Europe have shorter distances when transporting victims to advanced medical-care facilities.