As surely as winter follows summer, you will read headlines announcing the inevitable deaths resulting from blizzards. Many of the reported fatalities will concern motorists who become stuck in snowdrifts.
The same fate awaits a hunter who is surprised by an early winter storm while located a day’s hike from base camp. But extreme cold and blizzards are not the only dangers you will face this winter.
Hypothermia sneaking in
A review of medical records and news reports over the last 20 years reveals a picture quite different from what most survivalists envision as their major cold-weather challenge. Believe it or not, more deaths attributed to cold weather occurred during relatively mild temperatures—well above freezing.
The common mistake made by those victims was in not understanding the mechanics of hypothermia. In many cases, they wore adequate clothing, but couldn’t manage to stay warm by controlling their body temperatures. In ignorance, they allowed their body temperatures to cool without being aware of it. By the time their mistake was discovered it was too late to recapture the lost warmth.
What is the mysterious process called hypothermia which kills seemingly experienced outdoorsmen in moderate temperatures?
It is typified in newspaper stores, in the more familiar term “… he froze to death in sub-zero temperatures.” In temperatures above freezing, the news item would read, “Death was due to exposure.”
Although the reporters were probably not aware of it, the frozen victim and the one who died from exposure fell prey to the same cause—hypothermia.
Temperatures and excessive body heat loss
Look at a climate atlas of the world, and you may be surprised by the percent of landmass subject to cold temperatures. More surprising is the fact that most of the tropical lands on the map can also expose you to a fatal dose of hypothermia. This can occur anytime the temperature falls below the comfortable level, as during the night, winter season, or at higher elevations.
It happened to me in Hawaii at an elevation of only 2,500 feet. As you can see, the danger from cold can strike you almost anytime, anywhere, and especially on those occasions when you are least prepared for excessive body heat loss.
Cold weather preparation coven many subjects, all of which you will want to study: shelters, clothing, tents, boots, sleeping bags, stoves, nutrition, fire-making, food, hunting, snow emergency and travel, and more. But first, there is hypothermia, the cause for all this preparation.
A literal definition of this word might read, “A condition when the body temperature falls below 98.6 degrees F.”
To prevent hypothermia, your main objective is to stay warm and minimizing excessive body heat loss. You should never allow your body temperature to drop below normal. This is a key concept to remember, and there are two good reasons for stating what may seem to be obvious.
In almost all reported studies of hypothermia. the victims were not aware of their true condition. Secondly, once your body falls below the 98.6 degrees F. level, it requires much more heat and effort to get it back to normal than would have been used to merely maintain a normal temperature.
As you face excessive body heat loss, and the temperature falls, it creates a momentum that is difficult to reverse. By the time you realize your problem, it can be too late. The only way to avoid this danger is to understand how your body controls its temperature and heat production. This knowledge alone is the best single preparation you can make for cold weather survival.
Excessive Body Heat Loss
Hypothermia begins the moment your body begins to lose heat faster than it can be manufactured and retained. To prevent this, you must supply your cells with fuel (food) and allow only excess heat to leave your body. That’s all there is to survival in the cold. Just do those two things.
It sounds simple: “Carry a chocolate bar and wear a warm coat,” but staying warm can become a lot more complicated.
Man is most comfortable in a tropical climate. When he becomes uncomfortably cold, the blood vessels closest to the skin close down in order to send more blood and heat to the body’s central core. In other words, the body sacrifices the hands and feet in order to save the heart, liver, and lungs. This is why you suffer numb toes and fingers so quickly, which often leads to frostbite.
There is another effect of hypothermia, which you should keep in mind—especially if you aren’t in perfect health. As the reduced heat in your blood system cools your body cells, your entire health is suddenly imperiled. Each cell in every organ will operate in a half-hearted manner when it becomes cold.
This condition puts Murphy’s Law into full control: “Whatever can go wrong, will go wrong.”
No matter how healthy a specimen you may be, your body is predisposed to some weaknesses more than others. This weakness will be the first to show up. As you are dealing with excessive body heat loss and your body’s s temperature drops, symptoms will surface.
For example, if your lungs are harboring a pneumonia virus, your body’s defenses may become too weak to prevent the virus from multiplying. Cold is especially hard on your heart, lungs, and kidneys.
“Warm weather hypothermia” cases are common in temperatures between 30 and 60 degrees F. The reason such a paradox can occur is because the process is slow and gradual. By the time you become aware of your problem, it may be difficult to recapture your lost heat. When you become over-confident or careless, you may allow your body temperature to lower so gradually that you could become a “death from exposure” statistic.
It can’t be repeated too often, as Dr. Richard Besdine, a former professor at Harvard Medical School tells us, “Hypothermia can start whenever you begin to feel just a little uncomfortably cold.” He goes on to say that this could occur when the temperature around your skin falls to around 25 to 30 degrees F. below your normal body temperature.
For example, a middle-aged man in shirt sleeves will begin to feel cold at around 65 degrees or, if he is younger and healthier, at 60 degrees. When the thermometer reaches 30 degrees or 40 degrees, our middle-aged man will lose heat faster than he can produce it. This explains why so many older people are found dead in their homes from unexplained causes—victims of nothing more than exposure. or hypothermia.
Chances of facing
A question often raised is. “When does an ordinary backpack hike turn from fun into survival?”
The experts answer that by stating, “Don’t take chances. At the first hint of not being able to maintain warmth, terminate your present activity: stop your climb and return to base camp or interrupt your travel to bivouac. Make a shelter and fire.”
They also advise that if you suspect that you are close to a state of exhaustion while otherwise experiencing acceptable conditions, seek immediate rest and shelter.
Because you may not recognize danger signals in yourself, you and your companions should be trained to watch for them among yourselves. This is an important reason for carrying a rectal thermometer in your kit. Some people exhibit different symptoms of hypothermia at different stages. A rectal reading will show the exact status of hypothermia.
Everyone exploring the great outdoors should have knowledge of wilderness first aid basics.
Now that we’ve looked at the definition and dangers of hypothermia, the next step is to see how we can prevent it from happening to us. Harking back to the importance of controlling excessive body heat loss, let’s look at the six major causes of that loss.
You lose heat internally when your body’s available calories run low, requiring more food intake.
When your body produces more heat than it needs—as when you are exercising—you will perspire. When moisture from any source evaporates from your skin, the water vapor carries heat with it into the air. Wind or moving air accelerates evaporation, which leads to the wind-chill factor.
Your skin operates as a hot water radiator. Your skin’s surface blood vessels radiate heat waves into the air.
Heat flows from your skin and body directly through a cooler medium such as the ground, snow, metal or cold water. Immersion in a cold body of water can remove heat from your body 240 times the amount you might lose into the still air.
Heat radiated from your skin warms a layer of air surrounding your body. Air movement replaces that layer with cool air. The faster the air moves, the more heat you lose through the replacement of your warm air layer and the accelerated evaporation rate.
The air you exhale from your lungs is super-heated and the source of excessive body heat loss with every breath.
Now that the six sources of excessive heat loss have been pin-pointed, let’s go over each one and see how we can exercise some control over dangerous situations.
There are two ways to manufacture heat when dealing with excessive body heat loss: voluntary and involuntary.
Involuntary heat production goes on continuously through the metabolic process—the chemical burning of food fuels by your body cells.
Voluntary heat production comes through the exercise of your muscles. You can control your heat output by pacing your exercise. Jogging can raise your heat six times the normal basal rate.
Strenuous exertion for a short period can raise your energy level to 10 times normal. An exercise that will double your heat output can be sustained all day, such as walking.
Care must be taken that you don’t exert yourself beyond the amount of work necessary to maintain your body heat unless the situation becomes urgent. Exhaustion and hypothermia go hand-in-hand.
Your body might burn 2,000 calories per day while camping leisurely in one location. This would require only a couple of light meals a day to fuel your body, as long as you conserve your heat. But what about survival or expeditionary conditions which require the maximum energy production?
Most readers will recall reading that Eskimos eat whale and seal blubber to stay warm. Here’s why. Fat contains nine calories per gram, while sugar provides only half that amount. However, sugar has the advantage of releasing its energy much faster than fats.
There are various types of meals you can make at home to sustain your journey during the winter season and help you avoid excessive body heat loss. You can find my favorite winter trail foods in this article.
Caloric intake estimated to be adequate for cold regions ranges from around 4,000 to 6,000 calories per day, depending upon temperatures and activities. Based on the above figures, one pound of vegetable oil (fat) plus one pound of granulated sugar would give you a total of 5,821 calories—just about enough for one day’s rations. But that isn’t the whole story.
Your body also needs the total daily nutritional requirements included with those calories. This must be tailored to your individual needs and provided in maximum allowances. Protein, including the proper ration of essential amino acids, is needed to make daily repairs to overworked cells, joints, muscles, and organs.
Depending on your body weight, you would need between two to three ounces per day. There have been many stories published in outdoor magazines concerning protein starvation—especially while living off of rabbits, which have little fat on them.
The protein itself has nothing to do with starvation. You can starve from eating any one type of food because you are missing so many other essential nutritional elements. A high protein diet can provoke an existing health condition, but that would be fairly rare and a subject to discuss with your doctor in the course of a general examination.
Here’s the story on protein. If you eat too much protein, your body will eliminate some and store the remainder as fat. The body won’t use the protein as energy until it has burned up the carbohydrates and other fats already stored.
When your calories run low, the body will use the stored “protein-fat,” which serves you well until depleted. After that, your body will begin drawing protein from your cells to be used for energy. This is when the serious effects of starvation will appear.
Controlling fuel consumption also means controlling your eating habits by eating smaller meals more often: breakfast, mid-morning snack, lunch, mid-afternoon snack, and an evening meal to sustain you through a cold night.
For emergency tasks, such as climbing, a quickly absorbed simple carbohydrate is called for. Sugar or honey are perfect for fast energy. For long-range sustained energy, the complex carbohydrates are better: potatoes, grains, and starches, which release their energy slowly.
Make sure you carry some fat reserves by consuming food fats with one or two of your meals. You always want to stay ahead of your body’s fuel needs, or your furnace may go out.
Another aspect of control is accomplished by not forcing your body’s blood supply to do double duty. The digestion process requires the use of a considerable amount of blood. When you know a long rest period is coming up, a night’s sleep, for instance, plan to precede it with a larger meal, which includes the harder to digest foods such as protein and fat. Your muscles will appreciate not having to compete with your stomach for energy and blood.
Food input is the simplest and most pleasant task you will face in cold weather survival unless you run short, but that’s another story. Proper food intake will prevent excessive body heat loss.
Another topic that needs to be covered is the liquid intake required. This source will show you what beverages are recommended and which one should be avoided when dealing with hypothermia.
Excessive body heat loss through evaporation is the toughest problem you’ll face under survival conditions. In company with a breeze, evaporation is a highly efficient cooling mechanism, the same one used by your water-cooled air conditioner at home. In the wilderness, the water coolant can come from sweat, rain, snow, fog, streams, lakes or ocean.
You can provide protection from all of those sources except sweat. In the case of perspiration, you must attempt to control its cause and its escape. When the radiated heat from your body warms the air layer next to it, that layer provides insulation against the cold. But that protection is partially defeated when the warmth turns your sweat into a vapor which passes through the warm air layer and carries heat with it.
When wind is present, moisture and heat are removed rapidly. Your brain and body cells constantly juggle bodily functions, guided by temperature sensors in your skin, to maintain an internal temperature of 98.6 degrees. This figure can vary slightly in different individuals.
The importance of this delicate temperature balancing act goes back to the fact that your cells become “sick” and function at subpar efficiency when their temperature varies, even slightly. The evaporation system works well in warm air but tends to act against you in cold air.
You can prevent excess-perspiration by keeping your skin surface cool. This shouldn’t be hard in cold weather. The trick is to wear just enough clothes to keep you comfortably cool.
The other heat producer you must learn to control is exercise. First, you learn to pace yourself or remove enough clothing while exercising so that your sweat evaporates immediately into the air preventing your clothes from becoming soaked.
Least of Worries
Normally, radiation is the best of your heat loss worries. Heatwaves continually radiate from your body’s surface, but the loss isn’t critical and is relatively easy to control with clothing.
Keep in mind that the greatest radiated heat loss will come from your unprotected head. Always carry warm headgear even in mild weather.
Conduction, next to evaporation, can be the cause of your excessive body heat loss whenever your body comes in contact with a large cold mass. This loss can be easily prevented by putting distance between you and the cold objects.
Don’t sit on bare rocks; put padding between you and the ground or snow; be especially careful not to fall into water whether you’re in a boat of crossing a stream.
You need extra distance between your feet and the ground. Picture yourself as a hot water tank and your feet as the drain valve. Without proper insulation in your boots, your body heat drains through your feet into the ground. The same analogy applies when sleeping on the ground.
Convection, or wind currents, blow away heat from your body and right out of the clothing as well. Be prepared to put something between you and the wind. You can use a parka, tent, tree or anything which stops wind.
Wind removes your heat in two ways. It blows it away, and it speeds the evaporative process. More deaths are caused by the wind factor than from other cold conditions.
A tragedy often occurs during a mild night, which is accomplished by a moderate breeze. Without warm clothes you can easily survive a 50-degree emergency bivouac. But, if you experience a 20-mph wind, you face sub-freezing effects in what you expected to be a comfortable night.
Wind-chill charts are frequently published for outdoorsmen showing exactly what a windless temperature reading would be as the result of various wind speeds. These are of great help when trying to prevent excessive body heat loss.
If you’ve observed quarter-backs breaking from their huddle on a freezing afternoon, blowing on their hands, this is a demonstration of the amount of body heat lost through respiration. The more you exhale, the more heat you lose.
On the other hand, if you don’t inhale, you won’t receive the oxygen needed to make heat. But you can pace your breathing. If you find that you’re panting for breath, it may be a sign of overexertion and you risk the danger of exhaustion.
High elevations will cause panting, which warns you to move more slowly. You can save a little of your heat if you breathe through your nose. This will also force you to move at a more comfortable stride.
Excessive body heat loss can occur not only in polar or sub-polar regions, and you must be aware of how your body loses heat. More deaths attributed to cold weather occur during relatively mild temperatures. This article covered the six main causes of excessive body heat loss and how to mitigate their effect, but in the end, you’re the only one who can make a difference by preparing properly for an outdoor adventure.
This article has been written by James H. Redford MD for Prepper’s Will.