Respiratory Gas Shifts to Delay Asphyxiation in Critical Avalanche Burial: A Randomized Clinical Trial.

Importance: People who are critically buried by an avalanche typically die of asphyxia within 35 minutes, often making timely rescue impossible. The development of new strategies to delay asphyxiation is crucial to improve survival rates. Objective: To investigate the efficacy of a novel, user-carried avalanche safety device that delivers airflow from avalanche debris to the user's airway without requiring supplemental oxygen or a mouthpiece. Design, Setting, and Participants: This randomized, blinded, clinical trial was organized by 4 institutions and conducted at 1 field location in Italy from January to March 2023. Healthy volunteers aged 18 to 60 years were enrolled. Trial participants underwent a critical snow burial simulation while in a prone position covered by at least 50 cm of snow. Vital parameters were continuously monitored throughout the simulation to ensure participant safety and to collect physiological data. Interventions: Participants were randomized to the safety device group (using the Safeback SBX device) or the control group (using a sham device). The safety device group completed an unblinded control in which the participants who remained buried after 35 minutes were seamlessly transferred to the sham device. Main Outcomes and Measures: The primary outcome measure was the time to oxygen saturation as measured by pulse oximetry (Spo2) less than 80% (event) during 35 minutes of monitoring, comparing intervention and control groups. Secondary outcomes included oxygen and carbon dioxide concentrations at different distances in the snow. Results: Of 36 randomized participants, 24 performed and completed the trial and were included in the final analysis. The median (IQR) age was 27 (25-32) years, and 13 (54%) were male. In the safety device group, the median (IQR) burial duration was 35.0 (35.0-35.0) minutes and there were no events; in the control group, the median (IQR) burial duration was 6.4 (4.8-13.5) minutes and there were 7 events. The safety device group had a significantly lower risk of termination due to Spo2 less than 80% (P < .001 for both log-rank and Breslow tests). Carbon dioxide in the air pocket was 1.3% (95% CI, 1.0%-1.6%) vs 6.1% (95% CI, 5.1%-7.1%) and oxygen was 19.8% (95% CI, 19.5%-20.1%) vs 12.4% (95% CI, 11.2%-13.5%) at the same points in the safety device and control groups, respectively. Conclusions and Relevance: A user-carried avalanche safety device that delivers airflow from avalanche debris to the user's airways without requiring supplemental oxygen delayed critical hypoxemia and hypercapnia during simulated critical burial. Trial Registration: ClinicalTrials.gov Identifier: NCT05779540.