Comparison of avalanche survival patterns in Canada and Switzerland

Abstract

Background: Current recommendations for rescue and resuscitation of people buried in avalanches are based on Swiss avalanche survival data. We analyzed Canadian survival patterns and compared them with those from Switzerland.

Methods: We extracted relevant data for survivors and nonsurvivors of complete avalanche burials from Oct. 1, 1980, to Sept. 30, 2005, from Canadian and Swiss databases. We calculated survival curves for Canada with and without trauma-related deaths as well as for different outdoor activities and snow climates. We compared these curves with the Swiss survival curve.

Results: A total of 301 people in the Canadian database and 946 in the Swiss database met the inclusion criteria. The overall proportion of people who survived did not differ significantly between the two countries (46.2% [139/301] v. 46.9% [444/946]; p = 0.87). Significant differences were observed between the overall survival curves for the two countries (p = 0.001): compared with the Swiss curve, the Canadian curve showed a quicker drop at the early stages of burial and poorer survival associated with prolonged burial. The probability of survival fell quicker with trauma-related deaths and in denser snow climates. Poorer survival probabilities in the Canadian sample were offset by significantly quicker extrication (median duration of burial 18 minutes v. 35 minutes in the Swiss sample; p < 0.001).

Interpretation: Observed differences in avalanche survival curves between the Canadian and Swiss samples were associated with the prevalence of trauma and differences in snow climate. Although avoidance of avalanches remains paramount for survival, the earlier onset of asphyxia, especially in maritime snow climates, emphasizes the importance of prompt extrication, ideally within 10 minutes. Protective devices against trauma and better clinical skills in organized rescue may further improve survival.

Figure 1:

Overall survival curves for people completely buried in avalanches in Canada (n = 301) and Switzerland (n = 946) from Oct. 1, 1980, to Sept. 30, 2005, by duration of burial (Dümbgen comparison: p = 0.001). The dotted line represents the Canadian survival curve including only asphyxia-related deaths (n = 255).

Figure 2:

Survival curves in Canada by snow climate (maritime, n = 36; transitional, n = 132; and continental, n = 101) (Dümbgen comparison of continental v. transitional: p = 0.017; continental v. maritime: p = 0.008; transitional v. maritime: p = 0.33). Overall survival curves for the Canadian and Swiss samples (dotted lines) are shown for comparison.