If your feet are cold, put on your hat, and smile at the killer of the unprepared. Hypothermia has taken countless lives in the outdoors. Preparation and knowledge will keep you safe, warm and comfortable in the elements.
WHAT IS HYPOTHERMIA?
The prefix hypo means abnormally low and thermia, in this case, refers to body heat or temperature. Therefore hypothermia is a decrease in body core temperature to a level at which normal muscular and brain functions are impaired.
HOW IS HEAT LOST FROM THE BODY?
There are four routes which heat takes out of the body:
 | Radiation: Direct heat transfer to the environment.
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| Convection: Air next to the skin is warmed, it rises away from the body
and is replaced with cool air. Stop this by wearing a windproof outer layer.
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| Evaporation: Heat loss due to sweating; air breathed in is saturated with
body temperature vapor and breathed out. Both of these methods which vaporize
water cause great heat and water losses. Both are also increased with exercise.
Try to breathe through your nose to lessen the shock on your throat and lungs.
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| Conduction: Heat is directly removed from the body due to contact with colder materials, sitting on a rock or in the snow, jumping in water. So insulate yourself from direct contact with cold materials. Use your sleeping pad to sit on, or cut a smaller piece from the same material. |
HOW CAN OUR BODIES DEFEND AGAINST THE COLD?
Normal body temperature is 98.6 degrees F. and, given all these different ways of losing heat, how does your body stay warm? Luckily, even when we aren't prepared for the cold, our bodies have a few tricks for keeping us warm.
Increase heat production. Your body will increase your metabolism to meet the need for more heat. Muscular activity can also boost body heat, voluntary or not. Shivering is an involuntary reaction to increase body heat, but it's inefficient. Physical activity can greatly increase heat production. So, if you are cold, dance, jump and wiggle or do push-ups; in other words, stoke the fire, always eat plenty to keep the fire fueled up.
Cold hands mean that your body is trying to keep your heart warm. Think of the human body as two parts; a core and a shell. The core includes the vital internal organs such as the brain, heart, and lungs which must be kept at a constant temperature. The shell is comprised of the skin, muscles and legs which can tolerate relatively wide temperature variation. Because it is so important to maintain core temperature, the body will constrict the blood vessels to the surface of the body, thereby reducing the amount of blood flow to the body's outer layer. This way heat is kept deep within the body where it could otherwise be lost by convection, radiation and conduction.
The skin also tries to help by closing the pores and raising the hairs on the surface of the skin for insulation. This phenomena is commonly known as goose bumps. However, in general, we don't have the amount of fur that we used to, so look at goose bumps as a signal that your body is cold and do something about it.
If you don't eat, dress, and think warmly, then the following signs and symptoms might occur:
| 98 - 95F: Feel chilly, skin numbness, minor muscular impairment especially in hands, shivering begins. |
| 95 - 93 F: Muscular incoordination is obvious, weakness, stumbling, mild confusion, and apathy. |
| 93 - 90F: Gross muscular incoordination, frequent stumbling, inability to use hands, mental sluggishness, slow speech and thought, mild amnesia. |
| 90 - 86 F: Shivering stops, severe muscular incoordination and stiffness, inability to stand, incoherence, confusion, irrationality. |
| 86 - 82 F: Severe muscular rigidity, semi-conscious (barely able to arouse), pupil dilation, pulse virtually unapparent. |
| 82 - 78 F: Unconsciousness; death. |
Prevention is the best cure for hypothermia. If it does occur, get the victim moving. Give warm sugary liquids; e.g., cocoa, hot Jell-O, etc.