Do air pockets help avalanche survival?

The theoretical is obvious. If you have an air pocket you can breathe into after an avalanche, you should survive longer than if you don’t. This study intended to ascertain if this was true, as their hypothesis was that air pocket subjects would develop hypoxia, hypercarbia, and hypothermia, while those breathing outside air would simply develop hypothermia. Now, they did their study on piglets, as it is hard to get IRB approval for studies where the endpoint is asystole.

While the premise is good, unfortunately conditions outside the control of the researchers severely limited their study.

Eight piglets per group plus five pilot animals were planned; because of massive sensational media coverage, protests by animal activists and threats of violence and death towards the study team the study had to be terminated prematurely and only eight animal experiments were conducted

So they went ahead and used the 8, with 3 breathing from a 1L air pocket, 2 breathing from a 2L air pocket, and 3 breathing ambient air. All of them were anesthetized, intubated, and packed in snow during the measurement phase of the study.

A bigger problem with the study is what they did with their data. After collecting core temperature, cardiac output, paO2, paCO2, pH, and potassium (?), they then combined the 1L and 2L air pocket groups into one due to small sample size. They do include their data tables if you want to look at it yourself. It is full of interesting findings, such as measurable cardiac output on 6 of the 8 pigs during “asystole”. You’ll probably need to look at the raw data anyway, as the results figure online and in the pdf is impossible to read. You cannot tell which line is supposed to be which by looking at them.

The results were along the lines of what they were expecting. Yes, piglets with air pockets do worse than piglets with ambient air. And perhaps surprisingly, piglets with an air pocket develop hypoxia and loss of cardiac output relatively quickly (~10 min). The authors thankfully describe all the limitations of the study, and the difficulty in generalizing this to humans (surface ratio differences, general anesthetics present, higher metabolic rates, etc). While good proof of concept and need for further study, I’m not exactly sure what got this published in Resuscitation.

Paal P, Strapazzon G, Braun P, Ellmauer PP, Schroeder DC, Sumann G, Werner A, Wenzel V, Falk M, Brugger H. Factors affecting survival from avalanche burial–a randomised prospective porcine pilot study. Resuscitation. 2013 Feb;84(2):239-43 [PMID 22771873]

Further Reading

• Hensley J. Predicting survival after avalanches. EBM Gone Wild
• Hensley J. Do air pockets help avalanche survival? EBM Gone Wild
• Hensley J. Does that avalanche airbag really help? EBM Gone Wild
• Hensley J. Wear the helmet anyway. EBM Gone Wild
• Hensley J. Do ski helmets cause risk compensation?. EBM Gone Wild
• Hensley J. Treating serious frostbite. EBM Gone Wild