When an avalanche victim is critically buried, the presence or absence of snow blocking their nose and mouth has grave implications for survival and for the viability of avalanche safety technologies that prolong survival under the snow.
When I imagine myself buried in an avalanche, I always imagine the moment of coming to rest, the weight of the snow cementing around me, the claustrophobia of that moment. I imagine, vainly, that I might be able to control my panic and slow my breathing, hoping that I can prolong my survival under the snow. I never find myself imagining that in the turmoil of getting taken for a ride, my mouth and nose might become packed with snow, and in that moment when the cement sets up, I might not even have the option to breathe.
Whether or not a buried avalanche victim’s mouth and nose, their airway, is packed with snowy debris is a critical feature for prediction of their survival. Airway occlusion prevents any gas exchange with the surrounding snowpack, and the primary killer of the buried avalanche victim, lack of oxygen (hypoxia), sets in within minutes. While avalanche victims have been recovered alive after multiple hours buried with a large air pocket around their face, no survival beyond 35 minutes has ever been reported for a burial with an occluded airway.
But how often is the airway of a buried victim actually plugged with snow?
Both old and new avalanche safety technologies aim to prolong survival under the snow. Both the older Black Diamond Avalung and the new Safeback SBX system aim to prevent death by hypoxia by improving gas exchange with the victim’s surroundings, but neither technology can be effective if the mouth and nose are blocked. To a certain degree, the viability of these technologies depends on the frequency of that blockage.
(Interestingly, I am not aware of any technology that attempts to prevent occlusion of the airway).
A visual from Safeback illustrating how their SBX system functions.
A new study from the Eurac research group attempts to answer the question: How often is the airway of the critically buried avalanche victim blocked? The group performed a systematic review and meta-analaysis of existing studies and case reports to examine airway patency in critically buried avalanche victims. They screened 4109 existing studies identified with an inclusive search strategy, further reviewed 154 of those that might be relevant to the question, and then aggregated the results of 24 relevant studies with a few extra sources of data to create a pool of 566 cases of buried avalanche victims to address the question of airway patency.
The researchers divided victims into groups based on duration of burial (<35 min, >35 min, unknown) and subdivided those groups based on reported airway patency (obstructed, patent, unknown). Short burials comprised 19% of cases, and long burials 66%. Only 50% of cases had airway patency reported, while 65% reported the presence or absence of air pocket, and 78% reported survival status of the victim.
The bottom line is that 41% of critically buried avalanche victims in this study had a patent airway, and 12% had an obstructed airway. The remainder are unknown due to poor reporting. Victims with an obstructed airway were 4.7 times more likely to die. The overall mortality rate in the study was 63%, which is high compared to other studies of avalanche victims. The astute observer will probably have noticed that only 19% of victims in this study were buried <35 minutes. That statistic combined with the high mortality rate leads me (and the authors) to conclude that there is a bias towards reporting patients who have worse outcomes, as they are more likely to die or end up in hospital. This would bias the study toward underestimating the number of victims who either had a patent airway or who were rescued in under 15-18 minutes, when airway patency is less relevant. As with all studies of avalanche accidents, we can assume that there are many accidents, including critical burials, which are not reported and recorded.
My takeaway from this study is that safety devices that aim to improve our survival during burial by improving gas exchange are a viable concept. A significant fraction of the critically buried, at least 41%, have a patent airway and could benefit from this technology. Research on buried avalanche victims continues to rely on a retrospective collection of cases, which suffers from poor reporting and many missed cases. I look forward to seeing the Eurac group’s forthcoming publication on the efficacy of the Safeback SBX system, and you’ll see that here on The High Route as soon as it becomes available.
