Avalanche Flotation Devices - Keeping Things In Perspective
By Jeff Boyd, UIAGM ACMG CCFPEM ABEM, Mountain Guide, Emergency Physician.
As a mountain guide, an emergency physician and a member of the CMH Operations Team I have been working with the International Commission for Alpine Rescue (ICAR) on an array of different projects. ICAR is the forum for rescue organizations from 56 countries, has been in the game for 61 years and incorporates 4 specialty commissions - Alpine Medicine, Avalanche Rescue, Air Rescue and Terrestrial Rescue. As the official Canadian delegate to the commission for Alpine Medicine - aka the ICAR MedCom - I work on a spectrum of research on avalanche safety, rescue and resuscitation.
In 2007 we completed and published a study examining for benefit from avalanche safety devices and found that transceivers and airbags reduced mortality in the European population analyzed.(1) The author group did, however, identify the limitation that “this study reflects the specific situation of avalanche accidents in the European Alps and should not simply be transferred to other regions, where a different set of risk factors may operate”. One of those factors would be a difference in the relative risk of mortality from asphyxia versus other causes such as trauma, as the airbag used in our study only protects against asphyxia by reducing complete burials.
Therefore, we put together a highly-qualified Canadian research team to determine, as a primary objective, the relative contributions of trauma and asphyxia to avalanche mortality in our setting. We were blessed with a very comprehensive database of avalanche details from the Canadian Avalanche Centre and I ploughed painstakingly through boxes of files at the BC Coroners Service and the Alberta Medical Examiners Office for mortality data. In the 21 years considered we found 204 fatalities, a series 4 times larger than any previous study and very robust for meaningful conclusions. We found trauma was the cause of death in 24% of fatalities but another 10% of supposed asphyxia deaths suffered lethal trauma bringing the total proportion of trauma to 34%. This is 6 times greater than the reported rate of trauma in Europe. Trauma victims hit trees in 68% of cases and single-system trauma is inflicted on the chest in 46% and the head in 42% of cases. Surprisingly, only 48% of trauma fatalities are buried while, of course, all asphyxia victims are buried.
Helicat (helicopter and snowcat) skiers and snowboarders are 7 times more likely to suffer trauma as we spend a substantial amount of time in treed terrain and the proportion of asphyxia is reduced by rapidity of rescue. Conversely, snowmobilers suffer less trauma due to their preference for open terrain.
Our study(2) was published in March 2009 and in an accompanying editorial Professor Hermann Brugger, the president of the ICAR MedCom, recommended an airbag design that protected the chest, neck and head and additionally the wearing of helmets.(3)
We presented our data to the ICAR General Assembly in Zermatt in September 2009 and received considerable interest from countries, such as Norway, where recreationists spend time skiing and boarding in the trees. Professor Brugger then presented an international overview and concluded “safety devices should aim to prevent asphyxiation, but also should be designed to avoid traumatic injuries”.
The Canadian Avalanche Centre has initiated a prospective study examining for benefit from all varieties of safety devices but this study will take some time to accrue sufficient data to make statistically significant conclusions. Our study on European data took 14 years of reporting to come to reliable findings.
The evidence to date, indirect as it is, indicates that the airbag design should incorporate protection from trauma if they are to be effective in our setting, specifically helicat skiing using treed terrain in Western Canada. Considering all this we should proceed thoughtfully in the adoption of technologies such as airbags.
In the end, no energy should be diverted from the sophisticated CMH avalanche safety program that minimizes avalanche involvement in the first place.
Have a very enjoyable heliski season!
1. Brugger H, Etter HJ, Zweifel B, et al. The impact of avalanche rescue devices on survival. Resuscitation. 2007 Dec;75(3):476-83.
2. Boyd J, Haegeli P, Abu-Laban RB, Shuster M, Butt JC. Patterns of death among avalanche fatalities: a 21-year review. CMAJ. 2009 Mar 3;180(5):507-12.
3. Brugger H. Should strategies for care of avalanche victims change? CMAJ. 2009 Mar 3;180(5):491-2.
(The full-text versions of both our study and the editorial by Professor Brugger can be found on the open-access Canadian Medical Association Journal
by searching with the term “avalanche”)