Changes in systemic carbon dioxide levels during simulated avalanche burial using a one-way valve device: A randomized, double-blind, crossover trial.

INTRODUCTION

Mortality following complete avalanche burial remains high, primarily due to asphyxiation. Rebreathing-related CO₂ accumulation and oxygen depletion in the air pocket and surrounding snow are considered key mechanisms contributing to asphyxia. Artificial air pocket devices (AAPD) may mitigate this effect by separating exhaled from inhaled air. The present trial aimed to assess this effect in a simulated avalanche burial setting using continuous transcutaneous CO2 monitoring.

METHODS

In this randomized, double-blind, crossover trial, 11 healthy participants (3 female) underwent 2 simulated avalanche burials; one with, the other without (sham) a functional AAPD. Continuous measurements included: transcutaneous partial pressure of CO₂ (PtCO2), SpO2, respiratory rate, heart rate and end-tidal CO2/O2. Termination occurred i) per protocol after max. 45 min, ii) when predefined safety criteria were surpassed, iii) per participant request.

RESULTS

During burial PtCO2 rose steadily, reaching non-fatal levels. Compared to sham conditions, functional AAPD diminishes CO2-increase per timespan (+0.10 vs. +1.13 mmHg/min). In addition, burial time was markedly prolonged (44.3 vs. 6.4 min), and desaturation was prevented (96% vs. 75%) by the AAPD.

CONCLUSIONS

In this simulated avalanche burial trial, use of AAPD resulted in a significant reduction in CO2 accumulation and a substantial increase in tolerated burial time. This study provides evidence that neither low oxygen content within the snow-matrix itself, nor CO2-retention limit burial time. This implies that life-threatening hypoxemia is caused by both: rebreathing-related CO2 accumulation and progressive oxygen depletion of the surrounding snow.