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Affiliation
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Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy; International Commission for Alpine Emergency Medicine (ICAR MEDCOM), Kloten, Switzerland. |
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Abstract
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We read with interest the experimental study investigating the ability of an avalanche airbag with active deflation to create a post-burial air pocket (any space of air around the mouth and nose) thereby delaying asphyxiation and prolonging survival1. Candidates were placed in prone position into an artificial trough and were breathing in a mouthpiece of an inhalation/exhalation separator through two 1-way valves into the air-pocket created by the post-burial actively deflating avalanche airbag. All candidates except one completed the 60 minutes burial period with only one end-tidal CO2 above the normal range.
The pathophysiology of avalanche burial is a unique overlapping of trauma, hypoxia, hypercapnia and hypothermia. Outcomes hinge on the pre-accident state, injuries sustained in the avalanche, the total duration of burial and the possibility to breathe under snow debris. The European Resuscitation Council (ERC) guidelines for a prolonged avalanche-buried patient in cardiac arrest uses airway obstruction but not air pocket presence for the resuscitation algorithm2. In an experimental setting breathing under the snow with substantially increased work of breathing is possible for a few minutes even with only a “virtual” air pocket3. However, avalanche accident data from Austria showed that survival was higher in completely buried patients with patent airways and an air pocket4. For instance, 95% of the patients buried ≤15 minutes with an air pocket survived compared to 69% without; of the patients buried >15 minutes, 67% with an air pocket survived compared to 4% without4. The current study highlights the importance of the presence of a substantial air pocket (its exact size was not reported)1. Maintaining normal physiological oxygen and carbon dioxide levels during a complete burial is related to the size of the air pocket but also to the characteristics of the surrounding snow5. Snow contains a considerable amount of interstitial air and assuming that the air entrapped in the snow is accessible by the subjects breathing into an air pocket, a larger oxygen content in the surrounding snow could be available for prolonged breathing. It is known that gas diffuses through snow ...
Language: en |