Avalanche Survival in Broome

So that is the most ridiculous title that I have ever employed on this blog. Avalanches… Broome.. has Casey finally lost the plot? Well, maybe – but I blame Dr Morgenstern. He sent me an article to review for this month’s Journal Club and it forced me down a deep rabbit hole into a snowy academia that I never knew existed. Follow me, bring a shovel and an EPIRB.

Clearly avalanches are not a big killer in Broome. It is always 30-something Celsius and the tallest sand dune is a short jaunt over to the beach. So when I learned that skiers in Europe, Japan and Canada actually wear protective, inflatable backpacks with built in location beacons I was intrigued. From my innocent, outside perspective I was skeptical. Was this a real lifesaver? Or are some companies just profiting from the anxiety of winter sport enthusiasts? So to answer these unrequested questions – here are the stats. Stay tuned for next week’s podcast to see what we think about the latest tech in this space.

Most of the data used here comes out of the Swiss EURAC trial / data set which has been tracking avalanche rescues since 1981 and the results of over 1600 burials published by Rauch S, Brugger H, Falk M, Zweifel B, Strapazzon G, Albrecht R, Pietsch U. Avalanche Survival Rates in Switzerland, 1981–2020. JAMA Network Open. 2024;7(9):e2435253. doi:10.1001/jamanetworkopen.2024.35253. Published September 3, 2024.

There is also a paper comparing Canadian vs Swiss Survival here: Haegeli P, Falk M, Brugger H, Etter HJ, Boyd J. Comparison of avalanche survival patterns in Canada and Switzerland. CMAJ. 2011;183(7):789–795. doi:10.1503/cmaj.101435. Published April 19, 2011 (epub March 21, 2011). Interestingly – the “all comers” survival rates were almost identical 46% in both countries. The Canadians had more early “trauma related” deaths, but were a bit quicker to dig up survivors.

So lets review the survival curve, and what makes a difference.

The early deaths ( in the first few minutes) are due to trauma – that has nothing to do with snow burial, just the physics of flying down a mountain and being struck by debris. 10% death rate actually seems pretty good when you consider what is happening at high speed and how heavy trees and snow tend to be.

So 90 % still alive immediately after being buried but not killed by the impact. This is where it gets ugly. In the next 30 minutes another 60 percent will suffocate in the snow. The early survivors are those rescued by a companion on the scene. However, if you are waiting for a formal rescue party – don’t hold your breath (sic). The best rescue services were on the scene after the magic 30 minutes – around 35 – 45 minutes. At this point the survivors were those lucky enough to be buried with a decent air pocket nearby. They were able to chill out for longer and await death by hypothermia.

The next phase of death happens after 90 minutes. If you have air to breath and were not killed in the crash – you can last about an hour and a half on average before you get too cold and succumb to hypothermia. At the 2 hour mark we are down to single digits, less than 10 % survive here.

There is a new trick on the slopes for victims of hypothermic cardiac arrest – ECMO rewarming. This has shown a lot of benefit for other forms of hypothermic arrest however the stats in the context of being buried by snow are less appealing. The combination of burial / hypoxia and hypothermic arrest mean that we are still looking at less than 15% survival even if you get onto a warming circuit in time.

So – will an avalanche backpack save you – maybe… The main mechanism by which they help is by inflation and preventing deep burial in the snow. You tend to float on top of the snow fall if you are an big balloon. The newest models have built in fans that suck air from the surrounding micro-pockets in the snow and can create a breathable air supply …. Thus convert you from an “early suffocator” to one of the “late suffocators“. You will essentially have more time to contemplate your life choices… eg. should I have learned to scuba-dive instead? Where is my companion? What are the French 15 minutes slower than the Swiss rescue teams?

Ultimately – the best survival tip is to go skiing with a reliable companion who can dig well. Or stay in the perennial, tropical summer and avoid snow all together!.