What is Hypothermia?
Hypothermia, the number-one killer of most people lost in the mountains, is a condition in which the body loses heat faster than it can be produced and the body's temperature drops lower and lower. Heat loss is usually attributed to cold, wet, and wind, the CWW (SEE-dub-dub) of the mountains and normally develops when air temperature drops to between 50 and 35 degrees Fahrenheit.
Losing Body Heat
The body loses heat in five ways: Convection, Conduction, Respiration, Evaporation, and Radiation.
Convection: The primary function of clothing is to keep a layer of warm air next to the skin, but allows water vapor (perspiration) to pass outward. The body continually warms this layer of air close to the body. A wet suit uses this same theory, but when a person falls into the water you are chilled for a few moments before the water next to your skin is warmed by your body. A dry suit has less initial shock because water does not get inside to start with so the clothing you wear under the dry suit captures the air to retain your warmth. Heat is lost rapidly with the slightest breeze unless you wear a nylon or Gortex shell over your clothing to prevent the warm air from being lost. The cooling effect of wind chill is equal to that of much lower temperatures due to the increased evaporation and convection. You must have wind protection and good insulating value (dead air space) for your clothing to retain your body heat at a safe level.
Conduction: Heat is conducted away from the body when you are being rained on and large amounts of heat rapidly leave your body when you become wet through rain, snow, or perspiration. Conduction also happens when you lie on the ground, sit in the snow, or even hold cold equipment. Wool clothing, or newly designed synthetic materials (such as fiberfill) allow clothing to become wet with less heat loss. In very cold conditions, be sure to sit or sleep on a closed-cell insulating pad.
Respiration: Heat escapes when when you breathe out. By covering your mouth and nose area with wool (preferably) or cotton cloth will reduce this loss of heat.
Evaporation: Heat leaves your body as your skin dries. In addition, moisture expelled from the lungs also causes heat loss. Wear clothing that does not absorb moisture but will breathe and can be ventilated. Also carry clothing that can be added or removed in layers.
Radiation: The largest amount of body heat is radiated from uncovered skin, particularly through the head, neck, hands, and feet. Be sure to keep these areas adequately covered to prevent heat loss. Also, heat lost from the sides of the upper body is dangerous, as the sides are thin and close to the body's inner core.
It may take only 10 to 15 minutes of exposure to cold before the temperature of the heart and brain start to drop. So, when prospecting, never do so without a buddy--especially in cold weather--and be sure to keep a lookout for the early symptom of hypothermia.
In the Rockies, placer prospectors are, of course, involved with water. Hypothermia can be a threat in any water under 70 degrees Fahrenheit (F), especially without a wetsuit, because water conducts heat away from the body 25 times faster than air of the same temperature. Were you to remove your clothes and stand outside on an overcast 40-degree day for a half hour, you'd feel the same as being in 40-degree water for one minute, even wearing street clothes. Winds can chill the body as well. A 20-knot wind takes 40 degrees Fahrenheit down to a freezing wind-chill-factor of 30 degrees. Brrrr! When prospecting and you are exposed to wind, cold, or wetness, think "hypothermia" and keep a close watch on yourself and others for its symptoms.
The first and only sign you will have that you are on the verge of severe hypothermia is persistent shivering that you cannot stop by consciously relaxing your body. Your inner core temperature has dropped from 98.6 degrees F, is approaching 96.0 degrees, and your blood getting to your heart and brain has begun to cool. Even before it gets to this first sign, you must stop what you are doing and get warm. Get into a car with the heater on high or make camp and build a hot fire. If you wait until your shivering becomes violent and uncontrollable, you may not have enough control of your shaking hands to even build a fire.
The second stage of hypothermia is loss of coordination, stumbling, slurred speech, mental confusion, and the refusal and inability to recognize the problem in the first place. At this second stage, when your body's inner core has dropped to around 93.0 degrees F, all of these signs can occur at the same time. Of course, if you have the inability to recognize the problem, it is to late for you to do anything about it and to survive you must rely upon others to save you before you reach the next stage of hypothermia.
When your body's inner core temperature approaches 90 degrees F, the third and final stage of hypothermia is evidenced by unresponsiveness, decreased pulse rate, slowed breathing, cessation of shivering, physical collapse, and probably unconsciousness. If you are not treated immediately, death will quickly follow as the body's inner core temperature plunges below 85 degrees F and heart failure occurs.
Combating Chronic and Acute Hypothermia
Chronic hypothermia occurs over a long period of exposure from wind chill and wetness combined with exhaustion. The skin can become bluish-gray in color and violent shivering develops, giving way to muscle spasms, possible loss of the ability to control the use of your arms and legs, and drunken-like confusion. To avoid the effects of chronic hypothermia:
Acute hypothermia happens when you are in very cold water, especially when you fall into a cold water. When dealing with cold water, life expectancy is reduced significantly, but you can survive if you:
- Put on rain gear before you become wet.
- Stay dry.
- Keep moving.
- Wear several layers of light clothing.
- Wear wool, as it traps body heat even when wet.
- When dredging or sniping, wear a wet suit.
- Always wear a float-coat or personal flotation device (PFD) to insulate the body when near water.
- Keep your clothing on in the water to trap body heat.
- Don't thrash around, as flowing water conducts more heat away from your body.
- Draw your legs to your chest and wrap your arms around them in a huddle while rescue efforts are underway.