The dangers of back country skiing and snowmobiling are well known to the people of Montana. Newspaper articles caution about snow conditions, and unfortunately there are occasional reports of people being injured or dying as a result of avalanches. Classes are taught on how to recognize the conditions that might lead to an avalanche; and additional classes teach how to locate and attempt to save someone who has been buried in an avalanche. This article will present some of the medical background regarding what actually happens to someone caught in an avalanche.
The two main causes of death from avalanche are suffocation and blunt trauma. Suffocation is the most common and accounts for up to 75 percent of deaths. Blunt trauma accounts for most of the rest with a few being attributed to hypothermia. Suffocation is not due to a lack of air to breath, contrary to what most people think. In a few cases the mouth and airway can become packed with snow and prevent breathing, but more commonly the airway is open and usable. What has been shown to happen is that as the person breathes, they exhale CO2 which builds up around their head and face. They also melt some of the snow around their face with the warm breath. As this snow refreezes the CO2 is less able to diffuse away and oxygen is less able to diffuse inward. Over time, the person breathes a higher and higher concentration of CO2 and less O2 and becomes confused and then loses consciousness. The drive to breathe is also reduced with elevated CO2. The resultant decrease in O2 levels eventually causes death.
One proven technique to avoid this problem is a device called the Avalung. It is a simple set of tubes and valves with a mouthpiece. Breathing through the mouthpiece brings in well oxygenated air from the front of the victim, while the exhaled air containing the CO2 is directed outward behind them. Using this device people have survived being totally buried for several hours. Without such a device the standard outcome is 85 to 90 percent survival for 15 minutes, 30 percent at 30 minutes and only a few after an hour of being buried. There are two problems with the Avalung, the first is you have to have one with you, and the second is you have to get the mouthpiece into your mouth for it to work. Experienced backcountry skiers and snowmobilers do carry them and will often put the mouthpiece in prior to crossing a dangerous slope.
The second most common cause of avalanche mortality is blunt force trauma (about 24 percent). People can be violently thrown around by the rushing snow and ice, and can be thrown into rocks, trees or over cliffs. The result of these blunt injuries include internal bleeding from the liver, spleen and other organs, as well as fractures of the legs, arms, back and skull. Use of helmets can reduce the chance of head injury, but not much can be done about being thrown into a tree. First aid by others at the scene and rapid transport to a medical facility offer the best chance for survival.
Hypothermia can occur in people who have otherwise minor injuries. They may have lost parts of clothing and survival gear in the avalanche. They may also have lost their ability to get back to shelter through loss of their snowmobile or skis. As the body temperature falls they become confused and disoriented and become even less capable of helping themselves. As the body temperature falls, the heart rate slows, the blood pressure drops, breathing slows and death approaches. The best prevention for this problem is traveling with a group.
The recovery from hypothermia can be better than many people realize. The heart rate and breathing may become nearly undetectable. Despite this, it may be possible to revive the person. There is a saying in trauma care "they're not dead until they are warm and dead." In fact, recently developments in critical care for heart attack patients have involved cooling the patient for several days to allow the body to heal with less inflammation and stress. Some hypothermia victims can be rewarmed in a hospital slowly, with careful monitoring of their vital signs and make a full recovery.
In summary, the primary medical problems of an avalanche are suffocation and blunt trauma. The Avalung provides significant protection against suffocation. Transportation to a medical center is crucial for treatment of blunt trauma. Some patients with even profound hypothermia can be successfully revived.
Questions or comments can be addressed to Frederick M. Ilgenfritz, MD, FACS, c/o Bitterroot General & Vascular Surgery, 1150 Westwood Drive, Suite C, Hamilton, MT 59840 or visit www.bgvs.us.