The impact of avalanche rescue devices on survival

Prevalence of airway patency and air pocket in critically buried avalanche victims - a scoping review

INTRODUCTION

Survival of critically buried avalanche victims is directly dependent on the patency of the airway and the victims' ability to breathe. While guidelines and avalanche research have consistently emphasized on the importance of airway patency, there is a notable lack of evidence regarding its prevalence.

OBJECTIVE

The aim of this review is to provide insight into the prevalence of airway patency and air pocket in critically buried avalanche victims.

METHODS

A scoping review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline extension for scoping reviews. MEDLINE and Cochrane databases, as well as additional manual searching was performed to identify literature reporting data on airway patency and the presence of an air pocket in critically buried avalanche victims. After eliminating duplicates, we screened abstracts and main texts to identify eligible studies.

RESULTS

Of 4,109 studies identified 154 were eligible for further screening. Twenty-four publications and three additional data sources with a total number of 566 cases were included in this review. The proportion of short-term (< 35 min) to long-term burial (≥ 35 min) in the analysed studies was 19% and 66%, respectively. The burial duration remained unknown in 12% of cases. The prevalence of airway patency in critically buried avalanche victims was 41% while that of airway obstruction was 12%, with an overall rate of reporting as low as 50%. An air pocket was present in 19% of cases, absent in 46% and unknown in 35% of the cases.

CONCLUSION

The present study found that in critically buried avalanche victims patent airways were more than three times more prevalent than obstructed, with the airway status reported only in half of the cases. This high rate of airway patency supports the ongoing development and the effectiveness of avalanche rescue systems which oppose asphyxiation in critically buried avalanche victims. Further effort should be done to improve the documentation of airway patency and the presence of an air pocket in avalanche victims and to identify factors affecting the rate of airway obstruction.

Wilderness Medical Society Clinical Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents: 2024 Update

To provide guidance to the general public, clinicians, and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to revise the evidence-based guidelines for the prevention, rescue, and resuscitation of avalanche and nonavalanche snow burial victims. The original panel authored the Wilderness Medical Society Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents in 2017. A second panel was convened to update these guidelines and make recommendations based on quality of supporting evidence.

Avalanche Airbag Usage and Risk Attitudes of Backcountry Skiers and Snowboarders in the American West

INTRODUCTION

Backcountry skiers and snowboarders are increasingly using avalanche airbags to improve safety. New safety devices can cause risk compensation, the concept in which users take more risks given the larger safety margin provided by the device. This may limit overall benefits. We sought to elucidate attitudes toward risk-taking behaviors and risk compensation in backcountry users relating to avalanche airbags.

METHODS

A convenience sample of 144 backcountry skiers and snowboarders was surveyed after a backcountry tour in the Wasatch Mountains of Utah and the Tetons of Wyoming during the winter 2020-21 season. Demographic and experiential data were compared with risk propensity scores and attitudes toward risk compensation. Respondents were stratified into high-, medium-, and low-risk groupings based on risk propensity scores and whether an airbag was carried.

RESULTS

Thirty-two (22%) respondents carried an airbag. Airbag users were more likely to endorse risk compensation behavior, ski terrain over 30 degrees, and fall into the high-risk cohort. The high-risk cohort was also more likely to endorse risk compensation behavior than medium- and low-risk individuals.

CONCLUSIONS

Risk compensation was more prevalent in 2 groups: 1) those carrying an airbag and 2) those falling within the high-risk cohort. Given the prevalence of avalanche airbags, risk compensation should be considered alongside other human factors in avalanche safety and education so that users can mitigate these effects. Although risk compensation appears to be occurring, the magnitude of this effect remains unknown and likely does not obviate the safety benefits of the airbag altogether.

Electromagnetic Interference from Heated Gloves May Compromise Avalanche Transceiver Function

INTRODUCTION

Rapid location of avalanche victims by companions using avalanche transceivers is of utmost importance to prevent asphyxiation. The objective was to determine whether electromagnetic interference from heating elements in gloves worn by rescuers or victims can impair the receiving or transmitting function of avalanche beacons.

METHODS

Commercially available heated gloves from 3 different manufacturers were examined during a simulated search with 3 common brands of avalanche transceivers. Distance to target beacon at first signal detection and accuracy of direction to target, as indicated by the arrow from the direction indicator, were evaluated.

RESULTS

Preliminary tests showed that transmitting and receiving signals are degraded by electromagnetic interference caused by rectangular pulses emitted by activated heating elements. Field tests revealed significantly reduced distances of first signal detection when heated gloves were turned on near receiving avalanche transceivers (P<0.001; Wilcoxon signed-rank test). Decreased distance to target beacon ranged between 1.9 m (5%) and 41.5 m (94%) at first detection, depending on the avalanche transceiver used.

CONCLUSIONS

Avalanche transceivers are susceptible to electromagnetic interference from gloves with electric heating elements. We do not recommend using heated gloves when performing a transceiver search for avalanche victims because it can lead to a delay in rescue.

Effectiveness and Use of Avalanche Airbags in Mortality Reduction among Winter-Recreationists

RATIONALE FOR REVIEW

the number of backcountry skiers and snowboarder surged in the last years, especially during the COVID-19 pandemic, as ski resorts shut down. Inevitably, this led to an increase in avalanche-related injuries and death. As avalanche rescue device, avalanche airbags are increasingly becoming part of the standard winter mountaineering equipment. This study provides a review of available data and an updated perspective on avalanche airbags, discussing their function and efficacy to reduce mortality and their limitations.

KEY FINDINGS

causes of death in individuals caught by avalanches are multiple. Airbags seem to reduce mortality by decreasing chances of critical burial, the most determining risk factor. However, there is scarcity of reliable scientific research on the topic, and the way in which airbags reduce mortality and to what extent is still debated. Several elements seem to influence airbags efficacy, and their use still yields several limitations linked to manufacturing, proper use, users education, and risk compensation.

CONCLUSIONS/RECOMMENDATIONS

avalanche airbags seem to be an important tool in reducing mortality in backcountry expeditions. However, more research and standardized data collection is needed to fill the knowledge gap, mountain communities should promote adequate education of winter-recreationists on how to prevent and react to an avalanche, and on the correct use of airbags in combination with already available tools such as transceivers, probes and shovels, and manufacturing companies should ensure higher efficacy of the survival avalanche equipment for better prevention of burial, asphyxia, and trauma.

Avalanche Preparedness and Accident Analysis Among Backcountry Skier, Sidecountry, and Snowmobile Fatalities in the United States: 2009 to 2019

INTRODUCTION

While avalanche fatalities have remained relatively steady per year, data suggest a possible increase in sidecountry use and snowmobile fatalities. Limited information is known regarding the accident details and preparedness among different groups of backcountry users including snowmobiles, sidecountry, and backcountry skiers, and what specific factors could contribute to their fatalities.

METHODS

Avalanche fatality reports covering all US states posted by the Colorado Avalanche Information Center available online for 10 seasons (2009-2010 through 2018-2019 seasons) were analyzed for group size, specific equipment carried, burial depth, burial time, and other details. Only reports in the 3 following categories were included in the analysis: backcountry ski/snowboard, sidecountry ski/snowboard, and snowmobile/snowbike. These aspects were compared among the 3 tourer types using statistical analyses (ANOVA).

RESULTS

Two hundred and five fatalities were analyzed (n=32 sidecountry, n=91 skier/snowboard, n=82 snowmobile/snowbike). Using 2 preparedness scores, the ski/snowboard group had the greatest distribution of high scores when evaluated by equipment carried and group size, with significant differences per group (P<0.01). Of the fatalities that were buried, burial time was related to the tourer group (P=0.04), with the ski/snowboard group having the highest proportion of burials <15 min. Burial depth was significantly different among the 3 tourer groups, with snowmobiles buried the deepest on average (P<0.01).

CONCLUSIONS

Despite limited data available on fatalities, an analysis of preparedness suggests that backcountry skiers and snowboarders are more prepared for avalanche accidents compared to snowmobiles and sidecountry users when evaluated by equipment carried and group size.

Prevention of Hypothermia in the Aftermath of Natural Disasters in Areas at Risk of Avalanches, Earthquakes, Tsunamis and Floods

Throughout history, accidental hypothermia has accompanied natural disasters in cold, temperate, and even subtropical regions. We conducted a non-systematic review of the causes and means of preventing accidental hypothermia after natural disasters caused by avalanches, earthquakes, tsunamis, and floods. Before a disaster occurs, preventive measures are required, such as accurate disaster risk analysis for given areas, hazard mapping and warning, protecting existing structures within hazard zones to the greatest extent possible, building structures outside hazard zones, and organising rapid and effective rescue. After the event, post hoc analyses of failures, and implementation of corrective actions will reduce the risk of accidental hypothermia in future disasters.

Should Airbag Backpacks Be Standard Avalanche Safety Equipment?

Avalanche airbag backpacks have been shown to be effective at reducing avalanche mortality. However, they are yet to be considered standard avalanche safety equipment, which has long consisted of a transceiver, a shovel, and a probe. This is despite data showing that airbags reduce mortality by decreasing the likelihood of burial. In addition, airbags probably lessen trauma and possibly delay asphyxia. Moreover, the literature suggests airbags reduce mortality at a rate similar to transceivers. For those who work, volunteer, and recreate in avalanche terrain, airbags should be considered standard safety equipment. However, multiple barriers exist for universal adoption, including cost, size, weight, training burden, availability, risk tolerance, and lack of community support and recommendations from professional societies and associations.

Survival probability in avalanche victims with long burial (≥60 min): A retrospective study

BACKGROUND

The survival of completely buried victims in an avalanche mainly depends on burial duration. Knowledge is limited about survival probability after 60 min of complete burial.

AIM

We aimed to study the survival probability and prehospital characteristics of avalanche victims with long burial durations.

METHODS

We retrospectively included all completely buried avalanche victims with a burial duration of ≥60 min between 1997 and 2018 in Switzerland. Data were extracted from the registry of the Swiss Institute for Snow and Avalanche Research and the prehospital medical records of the physician-staffed helicopter emergency medical services. Avalanche victims buried for ≥24 h or with an unknown survival status were excluded. Survival probability was estimated by using the non-parametric Ayer-Turnbull method and logistic regression. The primary outcome was survival probability.

RESULTS

We identified 140 avalanche victims with a burial duration of ≥60 min, of whom 27 (19%) survived. Survival probability shows a slight decrease with increasing burial duration (23% after 60 min, to <6% after 1400 min, p = 0.13). Burial depth was deeper for those who died (100 cm vs 70 cm, p = 0.008). None of the survivors sustained CA during the prehospital phase.

CONCLUSIONS

The overall survival rate of 19% for completely buried avalanche victims with a long burial duration illustrates the importance of continuing rescue efforts. Avalanche victims in CA after long burial duration without obstructed airway, frozen body or obvious lethal trauma should be considered to be in hypothermic CA, with initiation of cardiopulmonary resuscitation and an evaluation for rewarming with extracorporeal life support.

Snow avalanche deaths in Switzerland from 1995 to 2014-Results of a nation-wide linkage study

Objectives

More than 20 people die each year in snow avalanches in Switzerland. Previous studies have primarily described these victims, but were not population based. We investigated sociodemographic factors for avalanche mortality between 1995 and 2014 in the entire Swiss resident population.

Design and methods

Within the Swiss National Cohort we ascertained avalanche deaths by anonymous data linkage with the avalanche accident database at the Swiss WSL Institute of Snow and Avalanche Research SLF. We calculated incidence rates, by dividing the number of deaths from avalanches by the number of person-years, and hazard ratios (HRs) for sociodemographic and economic characteristics using Cox proportional hazard models.

Results

The data linkage yielded 250 deaths from avalanche within the SNC population for the 20 years 1995 to 2014. The median distance between the place of residence and the place of the event (avalanche) was 61.1 km. Male gender, younger age (15–45 years), Swiss nationality, living in the Alpine regions, higher education, living in the highest socioeconomic quintile of neighbourhoods, being single, and living in a household with one or more children were associated with higher avalanche mortality rates. Furthermore, for younger persons (<40 years) the hazard of dying in an avalanche between 2005 and 2014 was significantly lower than in the years 1995 to 2004 (HR = 0.56, 95%-CI: 0.36–0.85).

Conclusion

Over a 20-year period in Switzerland, higher rates of dying in an avalanche were observed in men, in younger age groups, and persons with tertiary education, living in the highest socioeconomic quintile of neighbourhoods, and living in an Alpine region. For younger persons (<40 years), the hazard declined during the study period.

Extrication Times During Avalanche Companion Rescue: A Randomized Single-Blinded Manikin Study

Aims: This study aimed to determine the time needed for one or two companion rescuers to access, extricate, and deliver cardiopulmonary resuscitation (CPR) to a fully buried manikin during a simulated avalanche burial scenario. Materials and Methods: In this randomized, single-blinded study, 18 medical students were required to extricate a manikin manually from a simulated avalanche burial of 1 m in depth, either alone or in teams of two. Each participant performed three consecutive tests with the manikin in three different positions in random order. Results: Median time to first manikin contact was 2.5 minutes, median time to airway access 7.2 minutes, and median time to standard position for CPR 10.1 minutes. Overall, the number of rescuers (one compared to two rescuers, 10.5 minutes vs. 9.3 minutes; p = 0.686) and the burial position of the manikin (10.8 minutes vs. 10.6 minutes vs. 8.8 minutes; p = 0.428) had no influence on extrication times. Preexisting training (6.1 minutes vs. 11.0 minutes p = 0.006) and a learning effect obtained during the experiments (12.4 minutes the first test vs. 9.3 in the third test; p = 0.017) improved all extrication times. Conclusion: It takes an average of 7 minutes after location of a simulated avalanche victim, buried at a depth of 1 m, to free the airway, plus a further 3 minutes to initiate CPR in standard supine position. This is more than two-thirds of the 15 minutes considered necessary for successful companion avalanche rescue. Even minimal training significantly reduced extrication times. These findings emphasize the importance of regular practice in specific extrication techniques that should be part of any training in avalanche companion rescue.

Cut-off values of serum potassium and core temperature at hospital admission for extracorporeal rewarming of avalanche victims in cardiac arrest: A retrospective multi-centre study

AIM

Evidence of existing guidelines for the on-site triage of avalanche victims is limited and adherence suboptimal. This study attempted to find reliable cut-off values for the identification of hypothermic avalanche victims with reversible out-of-hospital cardiac arrest (OHCA) at hospital admission. This may enable hospitals to allocate extracorporeal life support (ECLS) resources more appropriately while increasing the proportion of survivors among rewarmed victims.

METHODS

All avalanche victims with OHCA admitted to seven centres in Europe capable of ECLS from 1995 to 2016 were included. Optimal cut-off values, for parameters identified by logistic regression, were determined by means of bootstrapping and exact binomial distribution and served to calculate sensitivity, rate of overtriage, positive and negative predictive values, and receiver operating curves.

RESULTS

In total, 103 avalanche victims with OHCA were included. Of the 103 patients 61 (58%) were rewarmed by ECLS. Six (10%) of the rewarmed patients survived whilst 55 (90%) died. We obtained optimal cut-off values of 7 mmol/L for serum potassium and 30 °C for core temperature.

CONCLUSION

For in-hospital triage of avalanche victims admitted with OHCA, serum potassium accurately predicts survival. The combination of the cut-offs 7 mmol/L for serum potassium and 30 °C for core temperature achieved the lowest overtriage rate (47%) and the highest positive predictive value (19%), with a sensitivity of 100% for survivors. The presence of vital signs at extrication is strongly associated with survival. For further optimisation of in-hospital triage, larger datasets are needed to include additional parameters.

Patient and rescuer safety: recommendations for dispatch and prioritization of rescue resources based on a retrospective study of Norwegian avalanche incidents 1996-2017

BACKGROUND

Avalanche emergency response should address current accident scenarios to optimize survival chances of victims and to keep rescuers safe. The purpose of this article is to present a basis for evaluation and necessary adjustments in dispatch, prioritization, and management of Norwegian avalanche rescue operations.

METHODS

This is the first peer-reviewed retrospective study of all Norwegian avalanche incidents registered by the two Joint Rescue Co-ordination Centers (JRCCs) in the period 1996-2017 that describes the characteristics and trends of rescue missions and victims.

RESULTS

The Norwegian JRCCs have registered 720 snow avalanche events, with a total of 568 avalanche victims, of which 120 (21%) died. Including those fatally injured, a total of 313 avalanche victims in 209 accidents were treated as patients (55%), and we saw > 1 patient in 24% of these operations. Norwegian avalanche victims were partially or completely recovered prior to the arrival of rescuers in 75% (n = 117) of all rescue operations. In the remaining 25% of cases, the rescue service located 62% (n = 55) of the avalanche victims visually or electronically. In 50% of the 720 incidents, rescuers spent time searching in avalanches with no victims.

CONCLUSIONS

This survey indicates that we have experienced a shift in Norwegian avalanche rescue: from search for missing persons in the avalanche debris to immediate medical care of already-located patients. The findings suggest that a stronger focus on both patient and rescuer safety is necessary. The patients must be ensured the right treatment at the right place at the right time and the allocation of rescue resources must reflect a need to reduce exposure in avalanche terrain, especially in cases with no affirmed victims. We present a flowchart with a recommended rescue response to avalanche accidents in Norway.

Avalanche Safety Practices Among Backcountry Skiers and Snowboarders in Jackson Hole in 2016

INTRODUCTION

Carrying standard safety gear (beacon, probe, and shovel), planning a route of descent, and recreating with companions can help to mitigate the risk of injury or death resulting from avalanches in the backcountry. The goal of this study was to identify factors associated with performance of these safety practices.

METHODS

A convenience sample of backcountry skiers and snowboarders was surveyed in 2016 at the backcountry gates of Jackson Hole Mountain Resort. Each participant was surveyed on characteristics including skill level, sex, age, prior avalanche education, and residency in the Jackson Hole area. Safety practices were also measured against avalanche hazard forecasts. Correlations were assessed using Fisher's exact testing.

RESULTS

A total of 334 participants were surveyed. Factors associated with carrying avalanche safety gear included higher expertise, being a resident of the Jackson Hole area, and prior avalanche education. Factors associated with having a planned route of descent included higher expertise and being a resident of the Jackson Hole area. Factors associated with recreating with companions included younger age and lower expertise. Sex had no association with any of the surveyed safety practices. Participants were less likely to carry avalanche safety gear on low avalanche hazard days.

CONCLUSIONS

Certain individual characteristics of backcountry skiers and snowboarders are associated with increased frequency of adherence to recommended safety practices. These findings suggest that particular categories of backcountry recreationists may benefit from further avalanche safety education. The results of this study could help direct future educational efforts among backcountry recreationists.

Wilderness Medical Society Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents

To provide guidance to clinicians and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the prevention, rescue, and medical management of avalanche and nonavalanche snow burial victims. Recommendations are graded on the basis of quality of supporting evidence according to the classification scheme of the American College of Chest Physicians.

The prehospital management of avalanche victims

Avalanche accidents are frequently lethal events with an overall mortality of 23%. Mortality increases dramatically to 50% in instances of complete burial. With modern day dense networks of ambulance services and rescue helicopters, health workers often become involved during the early stages of avalanche rescue. Historically, some of the most devastating avalanche accidents have involved military personnel. Armed forces are frequently deployed to mountain regions in order to train for mountain warfare or as part of ongoing conflicts. Furthermore, military units are frequently called to assist civilian organised rescue in avalanche rescue operations. It is therefore important that clinicians associated with units operating in mountain regions have an understanding of, the medical management of avalanche victims, and of the preceding rescue phase. The ensuing review of the available literature aims to describe the pathophysiology particular to avalanche victims and to outline a structured approach to the search, rescue and prehospital medical management.

The effectiveness of avalanche airbags

AIM

Asphyxia is the primary cause of death among avalanche victims. Avalanche airbags can lower mortality by directly reducing grade of burial, the single most important factor for survival. This study aims to provide an updated perspective on the effectiveness of this safety device.

METHODS

A retrospective analysis of avalanche accidents involving at least one airbag user between 1994 and 2012 in Austria, Canada, France, Norway, Slovakia, Switzerland and the United States. A multivariate analysis was used to calculate adjusted absolute risk reduction and estimate the effectiveness of airbags on grade of burial and mortality. A univariate analysis was used to examine causes of non-deployment.

RESULTS

Binomial linear regression models showed main effects for airbag use, avalanche size and injuries on critical burial, and for grade of burial, injuries and avalanche size on mortality. The adjusted risk of critical burial is 47% with non-inflated airbags and 20% with inflated airbags. The adjusted mortality is 44% for critically buried victims and 3% for non-critically buried victims. The adjusted absolute mortality reduction for inflated airbags is -11 percentage points (22% to 11%; 95% confidence interval: -4 to -18 percentage points) and adjusted risk ratio is 0.51 (95% confidence interval: 0.29 to 0.72). Overall non-inflation rate is 20%, 60% of which is attributed to deployment failure by the user.

CONCLUSION

Although the impact on survival is smaller than previously reported, these results confirm the effectiveness of airbags. Non-deployment remains the most considerable limitation to effectiveness. Development of standardized data collection protocols is encouraged to facilitate further research.

Fatalities Among Iranian High-altitude Outdoor Enthusiasts: Causes and Mechanisms

Purpose

This study was performed to determine the possible causes and mechanisms of fatalities among Iranian mountaineers during climbing.

Methods

By contacting several sources, deceased mountaineers were identified. Data about the causes and mechanism of death was retrospectively obtained using a standard questionnaire for each case.

Results

A total of 29 deaths were identified from March 2006 to June 2010. Deceased subjects had a mean age of 39 years (SD: 12.8, Range: 20-67). Falling was the most common accident leading to death of outdoor enthusiasts (n = 14, 48%). Asphyxia (n = 6, 24%) was the most common cause of death among the subjects, followed by heart attack, internal bleeding, cerebral hemorrhage and hypothermia (17%, 17%, 17% and 10%, respectively).

Conclusions

Our findings suggest that education of medical service providers of the climbing groups on facing victims in high altitude areas, where they have limited resources, can be particularly helpful. In addition, a national program to educate mountaineers might help to reduce fatalities.

Medical standards for mountain rescue operations using helicopters: official consensus recommendations of the International Commission for Mountain Emergency Medicine (ICAR MEDCOM)

The purpose of this article is to establish medical recommendations for safe and effective Helicopter Emergency Medical Systems (HEMS) in countries with a dedicated mountain rescue service. A nonsystematic search was undertaken and a consensus among members of International Commission for Mountain Emergency Medicine (ICAR Medcom) was reached. For the severely injured or ill patient, survival depends on approach time and quality of medical treatment by high-level providers. Helicopters can provide significant shortening of the times involved in mountain rescue. Safety is of utmost importance and everything possible should be done to minimize risk. Even in the mountainous environment, the patient should be reached as quickly as possible (optimally<20 min) and provided with on-site and en-route medical treatment according to international standards. The HEMS unit should be integrated into the Emergency Medical System of the region. All dispatchers should be aware of the specific problems encountered in mountainous areas. The nearest qualified HEMS team to the incident site, regardless of administrative boundaries, should be dispatched. The 'air rescue optimal crew' concept with its flexibility and adaptability of crewmembers ensures that all HEMS tasks can be performed. The helicopter and all equipment should be appropriate for the conditions and specific for mountain related emergencies. These recommendations, agreed by ICAR Medcom, establish recommendations for safe and effective HEMS in mountain rescue.

Comparison of avalanche survival patterns in Canada and Switzerland

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.

Patterns of death among avalanche fatalities: a 21-year review

BACKGROUND

Avalanches are a significant cause of winter recreational fatalities in mountain regions. The purpose of this study was to determine the relative contributions of trauma and asphyxia to avalanche deaths.

METHODS

We reviewed all avalanche fatalities between 1984 and 2005 that had been investigated by the offices of the British Columbia Coroners Service and the Chief Medical Examiner of Alberta. In addition, we searched the database of the Canadian Avalanche Centre for fatal avalanche details. We calculated injury severity scores for all victims who underwent autopsy.

RESULTS

There were 204 avalanche fatalities with mortality information over the 21-year study period. Of these, 117 victims underwent autopsy, and 87 underwent forensic external examination. Asphyxia caused 154 (75%) deaths. Trauma caused 48 (24%) deaths, with the rate of death from trauma ranging from 9% (4/44) for snowmobilers to 42% (5/12) for ice climbers. In addition, 13% (12/92) of the asphyxia victims who underwent autopsy had major trauma, defined as an injury severity score of greater than 15. Only 48% (23/48) of victims for whom trauma was the primary cause of death had been completely buried.

INTERPRETATION

Asphyxia and severe trauma caused most avalanche fatalities in western Canada. The relative rates differed between snowmobilers and those engaged in other mountain activities. Our findings should guide recommendations for safety devices, safety measures and resuscitation.