Interpreting the Updated Avalanche Survival Curve

Avalanche Survival Rates in Switzerland, 1981-2020 (2024)

The "Avalanche Survival Curve" is one of the most famous pieces of analysis in the avalanche rescue world, first published in 1994 based on Swiss avalanche accident data.

This was the first analysis that clarified how critical rescue time was for the improved survival of burial victims. In the initial study, the researchers found that buried victims had 15 minutes to survive before there was a rapid drop in survival rate, due to asphyxiation under the snow.

In the decades since its first publication, this curve has been shown in Avalanche courses and information nights around the world. All the while, skiers and snowboarders have continued to be caught in avalanches, building the dataset further.

The "updated" avalanche survival curve was published in JAMA in September, 2024. This blog gives our interpretations and key snippets from the published paper, using figures from the publication.

Updated Survival Curve

With 40 years of data from 1981 to 2020, the original research team has applied their methods to the wider dataset to reevaluate survival chances with more information. These are how their results compare to their original findings:

From this chart, and with some additional help from the paper, we can take the following learnings about avalanche survival:

10 minute rescue window, not 15

This study finds that, similar to analysis of Canadian accident data, that the "asphyxiation period" starts at 10 minutes, not 15 minutes. This means that there are 10 minutes to make a rescue with a 90% likelihood of avoiding asphyxial death, and by 30 minutes the likelihood of survival is reduced down to 30%.

Asphyxia is still the primary cause of death

Taken from the paper's Discussion section:

"In this study, the risk of dying from suffocation between 10 and 30 minutes of burial remained unchanged over the past 4 decades, highlighting the greatest challenge in the search and rescue of individuals critically buried by avalanche." (Rauch, Brugger & Falk, 2024)

Long term burial is more survivable

For those who manage to avoid asphixia and are alive for extended burials (>130 min), avalanche burial has become more survivable. This is assumed to be in large part due to the professionalization and advancement of rescue and care techniques to preserve the lives of those in critical condition after extremely long burial.

Survival by Decade

Comparing the four decades, the researchers looked at overall survivability in avalanches plotting burial survival rates of all victims an their overall survivability. The graph below shows the survival rate for each year, average for the decade, and a weighted moving average as a "trendline"

Comparing each decade, the researchers point out the following interpretations:

Overall survivability has improved

The comination of improved awareness, education, tools, and techniques for avalanche rescue have shown that the overall survival rate is much improved compared to the rate found in the 80's.

Survivability has plateaued since the 2000s

While there have been outlier years with improved survivability in the 10s, the 00s had the highest survivability overall, suggesting that optimizations in rescue made in these two decades may have helped some, but that they are relatively less impactful than innovations in the 80s and 90s when rescue best practices were less established.

Rescue Times by Decade

Knowing that rescue time is a critical factor in survival, the researchers looked into rescue times for each decade to see how they might influence the overall survival rate. The chart below looks at all accidents across the decades, charting when rescues were made by companion and professional rescuers.

Rescue times have not decreased since the 00s

In the chart, the blue (00s) and grey (10s) lines have been so close that there is no significant change in rescue times, whereas there were clear improvements from the 80s to the 90s, and from the 90s to the 00s.

Companion and pro rescue are both nearing optimization

In both Companion and Professional rescue, there has not been a significant improvement in rescue times since the 90s, suggesting that new technologies and techniques introduced over the last two decades have had a relatively low effect compared to the introduction of modern avalanche beacons and other widespread communication networks like cell phone towers

The full study is published in the Journal of the American Medical Association (JAMA), and was authored by emergency medical researchers Simon Rauch, Hermann Brugger, with statistician Markus Falk.

Thoughts from the authors, published in their press release:

"Time is the critical factor, and ten minutes is not long. Therefore, it's essential to understand that the survival chances in an avalanche burial are three times higher when excursion companions are able to dig out the victims, rather than when organized rescue teams are involved," explains Simon Rauch, the study's lead author and an emergency physician at Eurac Research.

"In 1994, we divided the survival curve into different phases and discovered that the first phase, when survival rate is very high, lasted up to 18 minutes. This became a global reference point in mountain rescue, but it now needs to be modified," says Hermann Brugger of Eurac Research, author of the original 1994 study and co-author of the current one.

Full Citation: Rauch S, Brugger H, Falk M, et al. Avalanche Survival Rates in Switzerland, 1981-2020. JAMA Netw Open. 2024;7(9):e2435253. doi:10.1001/jamanetworkopen.2024.35253

Other research conducted by members of this team:

Prevalence of Patent Airways in Critical Burial

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

Independent Medical Trial: Full Burial Testing

Eurac Research has conducted an independent medical trial of Safeback SBX to explore the extent to which the system can extend delay suffocation during burial.