Avalanche Survival Time Reduced According to the CMAJ

A recent scholarly journal article has found that victims in avalanche burial incidents who become completely buried are more prone to death than previously thought. In the wake of continued avalanche fatality incidents across the world this article does not debunk any myths that will offer greater hope, that when fully buried in a slide a person may have more survival time than previously thought. In fact, it does the exact opposite and speaks to actual differences in asphyxiation rates depending on snowpack, mountain region, and relative area where an avalanche occurred. This article comes from the Canadian Medical Association Journal and was conducted formally by Vancouver based scientist Dr. Pascal Haegeli, along with Markus Falk MSc, Hermann Brugger MD, Hans-Jürg Etter, and Jeff Boyd MBBS.

The thesis of the research essentially points to a discrepancy between North American and European burial survival times. Much of the available avalanche data that was looked at highlights that incidents commonly occur and are recorded above treeline in Switzerland versus slopes with trees in North America.  Therefore, data was scrutinized in Switzerland, and research shows that in North America many survival times are actually much shorter than in Switzerland. The idea is that because of the differences in snowpack and place between these two locales avalanche survival times are not uniform. In North America, the survival times were actually shown to be shorter.

While all of this information can be more intimately analysed by reading the whole paper linked here, here’s the abstract so you can get a better idea of what’s going on:

Background: Current recommendations for rescue and resuscitation of people buried in avalanches are based on Swiss avalanche sur- vival data. We analyzed Canadian survival patterns and compared them with those from Switzerland.

Methods: We extracted relevant data for sur- vivors and nonsurvivors of complete ava- lanche burials from Oct. 1, 1980, to Sept. 30, 2005, from Canadian and Swiss databases. We calculated survival curves for Canada with and without trauma-related deaths as well as for different outdoor activities and snow climates. We compared these curves with the Swiss sur- vival curve.

Results: A total of 301 people in the Canadian database and 946 in the Swiss database met the inclusion criteria. The overall proportion of people who survived did not differ signifi- cantly between the two countries (46.2% [139/301] v. 46.9% [444/946]; p = 0.87). Signifi- cant differences were observed between the overall survival curves for the two countries (p = 0.001): compared with the Swiss curve, the Canadian curve showed a quicker drop at the early stages of burial and poorer survival asso- ciated with prolonged burial. The probability of survival fell quicker with trauma-related deaths and in denser snow climates. Poorer survival probabilities in the Canadian sample were offset by significantly quicker extrication (median duration of burial 18 minutes v. 35 minutes in the Swiss sample; p < 0.001).

Interpretation: Observed differences in ava- lanche survival curves between the Canadian and Swiss samples were associated with the prevalence of trauma and differences in snow climate. Although avoidance of avalanches remains paramount for survival, the earlier onset of asphyxia, especially in maritime snow climates, emphasizes the importance of prompt extrication, ideally within 10 minutes. Protective devices against trauma and better clinical skills in organized rescue may further improve survival.

The major take home for us snow junkies is at one time 18 minutes was believed to be an acceptable survival time for fully buried avalanche victims. Now that research is saying ten minutes is more realistic. That’s an extraordinary shift in time.

The way this current research arrived at its conclusion was by first examining previous work done by researchers Falks and Brugger. This work looked at 946 avalanche fatalities from 1980 to 2005 in Switzerland. They found that 18 minutes was the average acceptable survival time across the incidents.

Dr. Pascal Haegeli then looked at 301 incidents in Canada. These incidents were all avalanche fatalities, but Dr. Haegeli  found 10 minutes was the common survival time as oppose to the 18 minutes Falks and Brugger found in their study.

What’s interesting is that the overall survivability remained almost the same for either country. In Canada the rate was 46.2%, while in Switzerland the rate came in at 46.9%. An intelligent follow up question might be, so how is the overall survivability rate so close when the survival time comes in at a whopping 8 minute difference?

Another major take home point, especially for snow sliders in maritime snowpacks, is that essentially this paper illuminates a very obvious yet unnerving attribute; it’s harder to take in oxygen through denser, wetter snow than lighter snow with more air in it. The study thus shows that asphyxia comes faster in maritime snowpacks than others.  Ultimately, the survival rate is the lowest for maritime snowpacks coming in at 41.7%. Continental snowpacks come in next at 46.6%, with a transitional snowpack  rounding out the list at 50.8%.

Another cruxy addition to this data is a study done by Jeff Boyd in 2009 speaking to the role trauma plays in avalanche incidents. This study found that about 24% of avalanche victims died from trauma, while 76% died from asphyxia. Another interesting number showed that about 33% of the non-survivors had induced some form of major trauma.Unfortunately, from reports in the lower 48 this season, trauma seems to be becoming an even higher statistic in terms of cause of avalanche fatality.

So what does this all mean? As stated above, this study shows that avalanche survival times are shorter than what was previously thought. It also points to maritime snowpacks yielding even worse survival times due to the commonly wetter snow conditions found in those regions.

Although this news isn’t what we’d like to be hearing the reality is that more people are out in the backcountry these days, and there are especially more skiers and riders pushing boundaries. However, safe protocol, solid partners, and proper decision making are still your best lines of defense. That said, it seems as though the argument for wearing an avalung that helps a buried victim breathe longer if buried and used properly in an incident, and an airbag-especially one that is built with trauma protective modifications in mind-makes that much more sense (hence the videos).