Effects of snow properties on humans breathing into an artificial air pocket - an experimental field study

Breathing under snow, e.g. while buried by a snow avalanche, is possible in the presence of an air pocket, but limited in time as hypoxia and hypercapnia rapidly develop. Snow properties influence levels of hypoxia and hypercapnia, but their effects on ventilation and oxygenation in humans are not fully elucidated yet. We report that in healthy subjects breathing into snow with an artificial air pocket, snow density had a direct influence on ventilation, oxygenation and exhaled CO₂. We found that a rapid decline in O₂ and increase in CO₂ were mainly associated with higher snow densities and led to premature interruption due to critical hypoxia (SpO₂ ≤ 75%). However, subjects in the low snow density group demonstrated a higher frequency of test interruptions than expected, due to clinical symptoms related to a rapid CO₂ accumulation in the air pocket. Snow properties determine the oxygen support by diffusion from the surrounding snow and the clearance of CO₂ by diffusion and absorption. Thus, snow properties are co-responsible for survival during avalanche burial.