Introduction
Survival time in an avalanche depends on factors such as patency of the airway and the volume of an airpocket. It also was suspected that the characteristics of snow, especially snow density, affects the development of hypoxia and hypercapnia.
Objective
To evaluate the influence of snow density on the development of hypoxia and hypercapnia in subjects breathing into an artificial airpocket.
Methods
Twelve male healthy subjects breathed through an airtight face mask and 40-cm tube into an artificial airpocket of 4 L. Every subject performed 3 tests on different days with variable snow densities (range 155–481 kg/m3). Symptoms, gas, and cardiovascular parameters were monitored for up to 30 minutes. Tests were interrupted at SpO2 <75%. Snow density was measured around the airpocket. A scatterplot of rate of CO2 decrease and O2 increase in the airpocket per snow density revealed 2 clusters (snow density ≤ or >250 kg/m3) that were confirmed by a 2-step cluster analysis. The second cluster then was divided by the median of about 400 kg/m3 into 2 subgroups. Test duration was analyzed by means of Kaplan-Meier estimator and log-rank test.
Results
Eighteen of 36 test subjects completed the test duration of 30 minutes. Test duration was different in the 3 groups of snow density (P < .05) and was shorter in the highest density group than in the other 2 groups (P < .05). Test duration in the lowest and middle snow density groups was not different (P > .05).
Conclusion
Snow density >250 kg/m3 was positively correlated with difference from baseline to maximum value of CO2 and negatively correlated with difference from baseline to minimum value of O2 levels. Unexpectedly, lower densities showed a different behavior on CO2 levels that could affect survival in avalanche-buried victims.