Hypothermia, The Cold Facts.
By Ron Hood
What is "hypothermia"?
First some of the things it isn't. It isn't a fear of needles. It isn't "feeling cold". It isn't that feeling you get when you play in the snow and your fingers are getting stiff. That kind of cold is much more superficial and can be easily controlled by the body when you stop your exposure. In fact it isn't even necessary for the temperatures to be at or below freezing for hypothermia to take place. There have been many instances of hypothermic death that took place in temperatures over 50 degrees f. What is necessary in order for Hypothermia to occur is that the body be unable to maintain it's operating temperature in the face of whatever heat loss process is in operation. Hypothermia is heat loss at the body core, and it results from exposure to cold with the addition of other heat loss mechanisms.
Typically we can say that four elements are present in each case of hypothermia, and without most of those four elements it almost never happens.
The four elements
The four elements leading to hypothermia are: Cold, Wind, Wetness and most important, a likely victim. It should be obvious that many of us have been exposed to cold ,wind and wetness without ever having experienced Hypothermia. Naturally this is because we were prepared for the conditions we were exposed to which leads us to another representation of hypothermia as "The killer of the unprepared".
One of the important goals of this chapter will be to give you the information you need to remove yourself from the ranks of the "unprepared". This will be easier if you understand more about the clinical aspects of hypothermia as well as the simple and effective methods we can use to survive the sometimes hostile forces of cold.
In order to be prepared we need to examine the four elements leading to hypothermia a bit more closely.
The second law of thermodynamics states in effect: "Heat must pass from the warmer body to the colder body."This simply means that when you expose yourself to the cold, you lose heat. The heat you are losing is probably heat that was generated by your body. Your body has a maximum limit to the amount of heat that it can produce, when the limit is reached, it can produce heat no faster. If heat is taken away faster than it is produced, the body will begin to cool.
You are already familiar with some of the effects of cold on the human body. For instance you know that as the body begins to lose heat faster than it is producing the heat it reacts by trying to reduce the rate of heat loss. This reduction in heat loss is brought about by a restricting the circulation in the surface of the skin. When this happens you begin to feel the cold. Later, with continued heat loss, the body will show other symptoms. Blood flow to the extremities will be reduced, giving you a sort of numbness and a reduction in coordination, strength and control, "I'm so cold my fingers are stiff." is an example of that closing down of blood to the muscles in the fingers. Continued exposure closes down more systems, the blood temperature throughout the body is reduced and the brain is affected. It is remarkable how sensitive the brain is to these temperature drops. A reduction of 20 Degrees f. at the brain will kill you while a drop of over 50 degrees (from normal) in the hands and feet will cause discomfort but no permanent damage.
Wind increases the cooling effect of cold or wetness. This occurs when the moving air encounters the thin layer of warm air clinging to your body. The moving air strips away the warm insulating layer and the body tries to generate another layer of warm air. As this new layer is removed the body transfers more heat to warm more air etc. This effect is known as this wind chill effect. Wind chill accounts for a very high percentage of deaths due to hypothermia. It is easy to overlook this factor and to wander unprepared for wind chill into what appears to be cold weather.
I mentioned that persons have died of hypothermia in temperatures around 50 degrees F. Part of the reason can be wind chill, take for instance an air temperature of 50 degrees, add the mind chilling effect of a 40 MPH wind and we have an effective temperature of 26 degrees. Many snow skiers have felt this effect when they find that although the temperature outside is low, in the sun it feels comfortable to the skin. Come the clouds, and a fast downhill run and the cold wind will put frost on the soul.
Another point I want to make is that for the wind to assist the cooling it is only necessary for the air to be moving relative to the warm body. The same wind chill effect applies when the body is moving rapidly through the air. A motorcyclist for instance, moving at 40 MPH on a windless day will experience the same chilling effect as a stationary person in a 40 MPH wind. Imagine if you will, what would happen to a motorcyclist who is driving along, cold because of the wind chill, and finds stiff fingers operating clutch and brake controls. Motorcyclists are frequent victims of hypothermia. They do not progress through the stages of hypothermia to actual death while astride their bikes, rather they simply lose some of their awareness, the control of their machines and die of something else. like compression during a collision.
If a person is adequately protected from the cooling effect of wind, there is a very much reduced chance of hypothermia. This person is Prepared for wind.
Wetness increases heat loss through evaporation. Think about the body for a moment. You already know what happens when you get very hot. You perspire. Your body doesn't do that simply because it likes to discharge water and increase your odor. Sweating is an adaptive process that enhances cooling. You know how good it feels to stand in front of a fan, or in the wind, on hot days, Cool right? Water increases the cooling effect of wind and vice versa, This water can come from any source, It may be the result of rain, immersion, perspiration, or from any other source. When the body is wet it loses heat much more rapidly.
Much more rapidly is something of an understatement. Studies suggest that water may conduct heat up to 240 times faster than dry air. No wonder the Eskimos aren't into swimming. It has been proven that survival times for an unprotected human in 35 degree water is listed in minutes. Heat is ripped from the body so rapidly that it loses its strength, coordination and the victim drowns.
A point I'd like to make here includes a survival tip I read in an antique survival manual. The manual was sold to early settlers for the journey across the continent. One suggestion found in the manual suggests that should you ever find yourself stormbound in an unprotected place, near an unfrozen lake, with the air temperature at or below freezing, you should climb into the obviously warmer lake and wait out the storm! The author reasoned that since the lake was unfrozen it should protect the body from the storm. I'd imagine that some folks tried it and discovered that it didn't work. No one complained because they didn't survive the technique. Stay dry, stay out of unfrozen lakes on cold days.
If you've got a waterproof covering of some sort and you use it to stay dry during a storm, then you are prepared for wetness. A suggestion in this vein. It is often inconvenient to carry a poncho or a tube tent when you take a short day hike Be prepared anyway. The lightest serviceable covering I know of is the large, heavy duty. trash bag.
To use it simply cut a 9" slit in the bottom, pull it over your body until your head sticks through the slit, and stay dry. It will protect you from wind and wetness.
The likely victim
The likely victim is the unprepared victim. If you know some of the factors that will contribute to your heat loss you can be better prepared. if you take some realistic steps you can remove yourself from the category altogether. Simple preparations such as the one I mentioned with the trash bag will improve your chances for survival. Think about it, How much does that trash bag cost? How heavy and awkward is it? It actually fits into your back pocket with only a small bulge.
Of course there are many other things you can carry as well as the trash bag to help you to survive. Most of these things will be small and cheap. But they help you to prepare, AND they help you to develop your survival mentality.
Time for a short digression. Remember the business of innovation? Consider that trash bag for a moment. What uses can it be put to? We already know that it will act as an effective rain shield. It can stop the wind and hold trash. Now consider these uses; if it is dark in color it can be used to melt snow on sunny but cold days. It will carry food plants for dinner. It can be used to carry pine needles and leaves back to camp for use as insulation in your bed. It can be used as a cozy hat or to carry water back to camp. It will just about perfectly fit over a loaded backpack to protects the contents from rain. Try thinking of some other uses for the bag. You may want to carry two of them with you whenever you go out.
Trash bags and wind aside, there is another part to being the likely victim. Panic and hysteria, Previously when we discussed this condition we decided that it can be partially controlled by orderly thought and directed action. Many persons who find themselves in a survival situation don't know the tricks you do. They will react mindlessly and try to travel vast distances with limited energy resources. This activity not only depletes their reserves, it often brings on other parts of the hypothermia problem. Their thoughtless actions result in sweat, exposure to the wind, and depletes their ability to ward off even minor environmental temperature changes. They are what can be called the "emotionally unprepared victims". The problem is neatly described by an old saying "In panic, a person can run for minutes, crawl for hours and then lie down from exhaustion for eternity.."
The likely victim then can include someone who is faced with the heat loss mechanisms of cold, wind and wetness to a minor degree. But with an emotional instability capable of magnifying the effects of simple heat loss much as both wind and wetness magnify the effects of the cold. All of this is part of the reason for developing your Positive Mental Attitude (PMA). Understanding the problem is half of the solution, doing something about it is the other half.
The Symptoms of Hypothermia
Once you know that hypothermia exists, and what conditions are likely to precede the problem, it becomes necessary to know how to recognize the symptoms. That old saw "Forewarned is Forearmed." fits nicely here since merely recognizing the symptoms can put you on the alert and set into motion the actions necessary to save a life. It is also important to realize that recognizing the symptoms of Hypothermia in yourself is sometimes difficult for reasons soon to be explained.
Experiments performed by various public and private institutions have tended to yield similar results. In most of these experiments Human beings were put through exposure to low temperatures while their blood pressure, temperature, reaction times, strength and motor skills were monitored. The tests have shown dramatic losses in the thinking abilities of the subjects while simple motor activities became nearly impossible. Total incapacitation almost always occurred before loss of consciousness.
During the course of the experiments certain facts became clear. Among those was an agreement on specific temperature ranges and symptoms, indicating the stages of hypothermia. In other words, researchers discovered that when the body cools to a certain point a specific symptom develops, Continued lowering of the temperature brings on the next set of symptoms. These symptoms are common to most subjects experiencing the same body core temperature. They also discovered that people have different abilities to resist the onset of hypothermia. Where one individual might drop into hypothermia at 50 degrees ambient, another in similar shape and condition, might not become hypothermic until the temperature dropped to 40 degrees.
I realize this fact is not especially shocking as we all know that people react differently to the same conditions. The reason I point it out is to indicate that the following information, while it has internal and symptomatic consistency, does not necessarily develop in each person at the same external temperature.
A "Normal" healthy human, in good condition with adequate energy reserves can maintain the body core temperature at it's "normal" 98. 6 F, while nude in 50F. air. The air of course is still and the body dry. At this point the body is pumping out heat as fast as it can and the core temperature is stable. Since the body heater is full on, for each degree the environmental temperature drops, the body core temperature will drop a corresponding degree.
Figure 1: Symptoms of Hypothermia Stage of Hypothermia Air Temp / Body Core Temp. Symptoms
....Air Temp / Body Temp.
(1 ) 47-50 F / 96-99 F = Uncontrollable shivering
(2 ) 42-46 F / 91-95 F = Violent shivering in waves. Poor coordination and stumbling
(3 ) 37-41 F / 86-90 F = Shivering ceases. Muscles are stiff or rigid. Impaired thinking and judgment
(4 ) 32-36F / 81-85 F = Rigidity continues, slowed pulse rate and respiration. Stupor, Immobility
(5 ) Below 32F / 78-80F = Unconsciousness, most reflexes cease, heart beat erratic, possible death
(6 ) Below 32 F / Below 78F = Cardiac Fibrillation. Edema & hemorrhage in the lungs. White foamy discharge from the lungs.
(7) Death !
While looking this over it is wise to keep in mind the fact that the temperatures given for the "Air temp." are approximate. Conditioning, fat accretions etc. all play a part in setting the final symptomatic display. Even the final temperature prior to death has been exceeded in both directions. Persons have survived lower internal temperatures and have died with higher ones. The symptoms however are very commonly associated with the stages as shown.
A few points need to be made here. You will notice that as an individual develops hypothermia the first symptoms of "uncontrollable shivering" occur. This is not that gentle "Brrrrr I'm cold" shiver. This is a good strong full body shiver of the tooth shattering variety. The victim feels cold inside. This shivering stage is the attempt by the body to generate heat with muscular activity of the involuntary variety. When the temperature continues to drop, the mechanisms in control of the shivering reduce their activity and the body reduces the flow of blood to most large muscle groups not necessary for survival. With a reduction in shivering comes the beginning of the end for reasoned action by the victim Also keep in mind the appearance of the victim to an observer. First the victim is shivering hard, then there is less shivering. This gives the impression that the victim is warming. After all, there is less shivering. As you read the symptoms again keep this fact in mind. You may not be able to tell immediately if the victim is warming or cooling.
When the shivering ceases during the third stage hypothermia, death is at the doorstep. A lone hypothermic has little chance of survival unless fortune provides some external source of heat as well as a reduction in heat loss. The wind stops, the sun drives the clouds apart, a bush bursts into flame while a cup of hot cocoa appears on the ground. "Lotsa luck".
Once the victim drops into the fourth stage hypothermia it's all over but the dying. Even if a rescue is affected there is a chance that death will still occur. Any first aid measures that take place after the victim becomes a hypothermic in the fourth stage, must be of an extreme sort administered in a specific manner. Simply covering the victim may delay death by a few minutes. Still there remains the chance of survival if certain steps are taken immediately by the rescuer. Even then much of the ability of the victim to survive is dependent upon the condition and the will of that victim. Injuries and illness lessen the likelihood of survival. Inappropriate or inadequate treatment may hasten death.
Hypothermia first aid
The treatment for hypothermia is a 1 - 2 - 3 matter and needn't be done in sequence for it to be effective. There may also be complications. First the basic steps.
1. Stop further heat loss : Remove the victim from the cold, cover and/or dry.
2. Add heat :Warm victim with full body contact or some external or internal source of heat.
3. Add fuel : Feed the victim. Hot sweet liquids are good. Cold fat or protein is not effective.
Unfortunately, taking these steps is often difficult and sometimes nearly impossible since Hypothermia frequently occurs in an emergency when there are few essential resources. If the victim has progressed into the later stages of hypothermia, simple exposure to heat and protection from the cold may have little effect. Obviously there are ways to successfully rescue a hypothermic but most of these depend on exotic techniques utilizing equipment rarely found in backpacks. The key to successful treatment of hypothermia will be to correct the problem in it's earliest stages. That calls for early recognition and treatment.
Another factor to be considered is that often the hypothermic does not recognize the symptoms and will sometimes resist treatment until it is almost too late. To gain the cooperation of the victim remember that the administration of hypothermia first aid does not have to be a dramatic gesture. One reason for this is the fact that the steps can be taken as conditions allow.
They can be simply a friendly act done as a favor, like loaning a jacket or stopping for shelter because "I'm getting too cold". Try to avoid the dramatic flair sometimes associated with life saving first aid. There is more to this so lets take a closer look at the steps, the combinations of steps and the cautions.
(1) Stop further heat loss
Clearly heat loss is the root cause of Hypothermia. If you stop further heat loss and if the overall condition of the victim is good, there is a strong possibility that the problem will disappear. It is wise to remember the conditions that led to the problem, cold wind and wetness. if the victim is only cold, covering up may do, but remember that cold alone is rarely the cause of the problem. As you know, wetness and wind will probably also be present. Get the victim to some sort of effective shelter. A tent, cabin, lean to, plastic sheet, rock shelter etc. will help. Remove the wet clothing, dry the victim and cover up.
Under some conditions total nudity is warmer than wet clothing. This is particularly true in dry windless cold. Wet cotton clothing is probably the worst thing to wear as cotton holds the water next to the skin, wicking moisture through it's structure, and increases your heat loss by as much as 90%. If the wet clothing is made of wool the clothing can be wrung out and put back on. Wool tends to retain warmth even when it is wet. Some new synthetic fabrics have the same qualities. Cover the victim's head! If the body cannot re-warm itself the victim may die. For this reason the remaining steps should be taken in all cases.
(2) Add Heat
Adding heat can occur in any way the second law of thermodynamics will allow (Heat must pass from the warmer body to the colder body). The only restrictions placed on re-warming involve the rate of reheating the body. Immersion of the body in molten lava is one of the many techniques considered a no-no. Oddly enough some of the methods commonly used for re-warming are equally dangerous. These well meaning techniques include exposing the victim to intense local heat in the form of a blazing fire.
When an intense form of heat, such as a fire, directs its energy upon one bare area of the body, unfortunate consequences can arise. To understand these consequences we must first remember what happens to the body as the heat loss begins. One of the responses to cold was a general constriction of the blood vessels in the skin and extremities. This blood may reach temperatures as low as 40 degrees and is slowly circulated as a form of insulation for the body core. If a strong source of heat, not just warmth, begins to raise the skin temperature to an uncomfortable level, the brain reacts by causing the heat to be drawn away into the skin through the circulatory system to the core. If the heat is intense and local, say an area the size of your chest, very little actual warmth will have been transferred to the blood. The slightly heated but fatally cold blood travels directly to the body core bringing with it a massive slug of almost ice cold blood. The delicate internal temperature balance is destroyed, the temperature drops below 78 degrees and the victim dies. OOOPS……
Therefore, when adding heat to the hypothermic, avoid intense local heating. A gradual raising of the temperature is preferred. Often this can be accomplished without a heating fire. If a heating fire is available, feel free to use it but be certain that the victim is heated as evenly as possible through some intervening layers of fabric.
Ideally the external source of heat should be at or only slightly warmer than the normal body temperature and should be transferred to the entire body. A warm bath is acceptable if it happens to be available and if the "after drop" in core temperature is watched closely. "After drop" is the drop in core temperature we discussed as related to a sudden increase in skin temperature resulting from sudden exposure to high temperatures.
Another way to accomplish whole body warming while in the field is to strip the victim to the skin and put the person into a pre-warmed sleeping bag. If conditions allow, two other persons of normal temperature should also strip and crawl into the bag with the victim. Heat gained through conduction and imagination will be rapid. If a sleeping bag is not available, use blankets or mink. Even one extra naked body in the bag will speed recovery. One caveat to keep in mind, the rescuer should not endanger him or her self by the rewarming process. Body contact rewarming is best used when there are other fully functioning individuals in the party.
To further raise the temperature and increase the speed of the rewarming process it is also wise to induce the victim to drink warm liquids. This will tend to raise the temperature at the core. These drinks should be sweet (no diet sweeteners please) if at all possible. The victim will need energy in order to feed the rewarming process. More on these drinks later.
If there is no possibility for the dual nude system in the bag, or if the victim is alone and trying to gain warmth in the bag. Try hot water in a canteen, warming stones etc. to build heat. Keep in mind the fact that just as clothing insulates us from cold, it also slows down our absorption of heat from external sources. The victim will warm faster while nude in a warm environment than clothed in that same environment.
Once the victim has regained complete awareness, continue the hot liquids. It takes time to recover from hypothermia, full recovery may take hours or even days. Hypothermia can easily reoccur while the victim is weak. If the hypothermic is unconscious, death is close at hand. Only the most drastic steps are likely to be successful. Even so you should attempt to revive the victim using the resources at hand. Many times the effort has paid off.
(3) Add Fuel
Adding fuel is really very simple. You are providing the body with a generous store of power with which to reheat. The power should come in some easily assimilated form. Warm sweet liquids are a favorite because the effect is almost immediate and most hypothermics will accept them. Sweet foods like candies are next. Many sugars are releasing their energy to the body within 15 minutes of consumption.
While feeding you should consider the types of foods the victim can easily use since some items containing protein and fat require considerable time and effort for digestion. Stay away from them unless significant amounts of heat and carbohydrates are immediately available. Hot soup with noodles is acceptable, Hot cocoa, hot dextrose or hot coffee or tea with plenty of sugar is acceptable. Beef jerky or a cube of butter is almost useless in the short term. Any form of alcohol is always unacceptable.
The Unconscious Victim
Since the unconscious victim is usually unable to swallow, it is unwise to try to force liquids, you may violate the first of the rule of threes "Three minutes without air" by drowning the person in noodle soup. Still, to revive that cold but alive body, heat must be brought into the core. How to do that? One way, a method used by some search and rescue teams is to offer heat absorption through the lungs. Presumably the living victim will continue to breathe. If the air that person is breathing is prewarmed and highly oxygenated a good deal of blood can be quickly heated and recovery can begin. The teams carry heated air respirators.
These devices utilize a flameless low temperature chemical process to heat air carried in a small bottle. The device is seldom carried by normal backpackers but there is a field expedient. It may not be as efficient but it can work. Try mouth-to-mouth resuscitation with the unconscious victim. Your warm air, body contact as well as a warm protected environment might be enough to successfully reverse the problem. Another possibility utilizes one or two of those chemical "HeatPacks". Wrap them in a thin layer of dry fabric and place them on the Carotid arteries on the sides of the neck just below the chin. These can heat the blood and air providing heat calories directly to the core.
Other methods of adding heat to the body core exist and work with varying degrees of efficiency. Some of these techniques may seem a bit distasteful but the act of bringing someone back from the doors of death is a tasty challenge. The methods include such things as warm enemas and warm liquids pumped directly into the stomach. Gaaaa! Both of these techniques have been field expedients over the centuries and may be worth attempting as a last ditch effort. Both were said to have been used by Hannibal when he crossed the Alps. With the unconscious victim either method will help raise the temperature.
A few words about each method seems to be in order. If you choose to try to administer heat to your victim by utilizing an enema, you have made a tough decision. Many obvious preparations are necessary with regards to sanitation etc. and I hope for your sake the process is successful and that the victim is good natured.
Pumping a warm liquid into the stomach is reasonably simple. Obtain a short piece of small diameter tubing, a size that will allow air passage while it is in place. Slide the tube down the throat into the stomach. Blow or suck on the tube to be certain the tube is in the stomach and not in one of the lungs. Blowing will cause a bubbling sound in the stomach, sucking on the tube will lead to predictable results. It is also possible to press on the stomach while watching the tube, Fluid indicates the proper position in the stomach or an impossibly filled lung. Air issuing from the tube indicates a lung.
After installing the tube and checking it's location you may force hot sweet liquids directly into the stomach. While installing the liquid it is wise to check the breathing frequently to certify that the lungs are neither being filled or prevented from operating. injection of the liquid can be done by mouth. Do not pump more than one quart into the stomach and be very careful as the victim may vomit and subsequently inhale the fluid. When the victim regains consciousness continue to offer warm drink. At this point you may notice that the symptoms of hypothermia are beginning to reoccur in reverse order. Sometimes the person will simply "come out of it." with no reversal of symptoms
Treating an unconscious victim is a difficult problem to deal with. I suggest that you never allow the problem to develop to that point by treating it early.
Disclaimer: I do not recommend the use of the stomach tube or enema system. They are included here only to offer some historical and theoretical techniques. These methods should only be attempted by trained medical personnel.
A Last Shot
We've all heard how a "shot" of booze can "warm the spirit". I suppose this is true in a very literal way. Alcohol to a hypothermic warms the spirit for it's journey to the next incarnation. You know how much warmer you feel when you drink alcoholic beverages while you're cold. As you probably already know, that heat is only a momentary sensation brought to you at the expense of the heat energy being stored in the core of the body.
This effect is caused by a process called "dilation" which is the opening of blood vessels in the skin and extremities and is brought about by alcohol. The heat thus released results in the sensation of warmth without any actual additional heat being generated. Don't drink for warmth. Many hypothermia deaths are alcohol or drug related.
Abstinence is wise with regards to any of the so called "recreational drugs". The combination of cold, lowered resistance to drug effects, and other unknown complications may reduce your ability to cope with the cold.
Prevention of hypothermia
Prevention of hypothermia is a relatively simple matter. Be prepared for the worst possible conditions you are likely to encounter. A simple theory but sometimes ignored as too inconvenient. For this reason the preparations that you make should be simple, effective, and convenient.
A major part of the preparations you have already made. You have become familiar with the problems related to cold exposure. You know how to recognize hypothermia should it affect yourself or one of your party. You know what to do to treat it. In fact, by knowing what to do in the treatment you have really picked up the basics of prevention. Here are some more ideas that may be of assistance to you as you avoid the chilling grip of Hypothermia.
You will be better able to protect yourself from the cold if you have a good basic grasp of the heat loss and gain mechanisms for the body. Most of these we've already discussed but lets put them in a slightly different form so we can deal with them effectively.
Heat comes to the body from two basic sources. Internal sources of heat such as the heat produced by your metabolism and by muscular activity, and external sources such as fire, sunlight and thermonuclear bombs.
Internal sources of heat depend upon the energy you have stored in your body battery. If you have a fully charged biological "battery" you can generate heat for many hours. As the power in this reserve is depleted or as the temperature and associated events, robs you of essential energy, your body begins to react in a specified manner to generate more heat. The most common method of generating heat is an involuntary contraction of the muscles. The contraction is called "shivering" and is associated with hypothermia when it becomes intense enough. Shivering produces heat through an increased metabolic rate and through friction within the muscles themselves. It also requires a great deal of energy to perform. It is not normally wise to sit quietly in the cold waiting for your body to convulse and generate heat. A simpler method would be to take advantage of voluntary muscular contractions.
Voluntary muscular contractions are often called exercise. If you begin to get cold, don't wait for your body to become so chilled that it shivers. Instead do exercises to produce heat. In a survival situation this may mean that you have to "keep moving" throughout the night in order to survive. This movement must be carefully done so that you do not become totally exhausted and slump into a mindless pile half way through the night.
Voluntary muscular activity can include movement of the legs, of the chest muscles and the arms. Slow and deliberate walking in a sheltered place may make the difference between life and death. Another way, almost as efficient in its heat production, and much easier to control, is the simple muscular contractions called "isometrics". In this exercise the survivalist simply forces one set of muscles to resist the movement of another opposing set i,e. One hand grips the other, one arm forces itself down while the other arm forces it's way up. Another technique is to place palm against palm and push the hands together as if you are trying to crush a walnut held between the hands. A few moments of this type of action will develop heat energy without a significant rise in the actual metabolic rate. Isometrics are unlikely to force perspiration or raise the respiration rate. Isometrics can also be performed in tight spaces if room is at a premium.
Another advantage of isometrics over jumping jacks, running in place, push ups and disco dancing, is the reduction of "Air Pumping". Air pumping takes place during active exercise. Air pumping is when the air that is warm and close to the skin, is pumped out into the cold by the alternate ballooning and collapsing of the insulating garment. That pumped out heat may be essential to your survival and efforts must be made to retain it. Slow exercise, done constantly and consistently as needed will help. If you find that you cannot stay still for some reason and you must move about to stay warm, by all means do so. First take some precautions.
If the pumping of warm air is taking place, that means there is some sort of insulation leak. These leaks most often appear in places like the collar of the shirt, or coat, and down through the pant cuffs. The simple prevention is to tighten all the areas that will allow heat loss to occur. The pant cuffs can be tied loosely around the ankles, or simply stuffed into the tops of the sox. Sleeves can be buttoned and tied loosely with cord. The collar should be fully extended over the neck.
The head and neck area is the most frequently overlooked heat loss area of the body. It is also one of the easiest areas to protect. You may have heard the old dictum "If your feet are cold, cover your head" this is a highly accurate analysis of the response of the body to cold.
You already know that as the body gets cold, circulation to the extremities is reduced and you feel cold. The feet are often the first extremities to feel this cut off. If the head is uncovered a great deal of heat energy is being radiated into space and that energy must be made up in some manner. Reduction of heat loss in other less important areas is the physiological response. If the feet feel cold and the head is uncovered, cover the head. The extra energy will now be sent back to the feet, warming them. Many backpackers refuse to wear a hat until they feel miserable. They depend upon their thick down jackets for protection. Forget it, people have dropped into hypothermia while wrapped in down jackets because their heads were bare.
Remember, the head and neck can radiate as much as 60% of the body's heat production. This is a direct loss and can be easily reversed. If you find you have no hat, make one. If you happen to be wearing two pairs of sox but have no hat, remove one pair of sox, replace your boots and tie them lightly so as not to restrict blood flow to the skin (Loose boots also offer more insulation in the form of trapped air than do tight boots). Take the two sox and try to pull one over your head. If it doesn't fit, cut both socks and stitch the two halves together to make a hat. Stuff the hat with extra insulation. Where do you get the thread and needle? Remember innovation.
Since we are dealing with internal sources of heat and the conservation of that heat it is useful to remember a few other points. Almost any dry material can be used as insulation. This is to say that you can use dry leaves, cattail tips, pieces of fabric, feathers and fur between the layers of your clothing to reduce heat loss. If you are wearing a long sleeve shirt and long pants, the pants can be sealed as has already been mentioned. Then a fill of dry leaves or other material suitable for insulation, can be poured down the pants. This will be uncomfortable and temporary but the additional insulation may make the difference between seeing only the night and seeing the morning too. Fill the shirt with the same material. Almost anything can be used to increase the insulating value of clothing as long as it is dry.
If you have no gloves and your hands are cold, your head gets first dibs on the sox. You need to survive, not have comfortable hands. One way to protect your hands is obvious, put them into your pockets. You can also pull your arms up into the shirt so that the arms and hands are close to the body. By removing your arms from the cold environment you have acted to reduce heat loss through radiation.
Don't overlook anything you have with you as possible insulation. If you happen to be carrying a small pack but are without storm gear, the contents of the pack should be inspected for possible use as insulation. In addition the pack itself can be used as a short shelter. You can slide your feet into the pack and protect the lower portion of the body. It may also be useful as a seat to raise you off the ground. This too will reduce heat loss through conduction.
Stop.... Did you notice? there are more ways to lose heat than just the three we already mentioned, cold, wind and wetness. Remember, there are five active heat loss mechanisms working to deprive the body of it's energy.
The five heat loss mechanisms, revisited
I cannot stress the importance of this issue too much. Remember, the five ways the body can give up energy are heat loss through conduction, convection, radiation, respiration and perspiration. Now that the considerations for body temperature maintenance are more refined. Lets take a quick look at the big five.
Heat loss through conduction is the result of contact between your warmer body and some colder object or body. A good example is conduction heat loss to the ground. Countless times I've seen people spend significant amounts of time constructing a wind tight, rain protected shelter with no ground insulation. They always seem to survive the night but mostly they feel like hell in the morning and complain of stiff cramped muscles. The blood flow to those cold muscles was cut down by the reactions to cold that you already know. When blood flow as restored in the warmer morning hours, stiffness and aches are common. In extreme cases, conduction loss can kill.
Convection heat loss is the wind chill effect we've spent so much time with. The cooling effect of the wind upon the body is a serious survival factor.
Radiation heat loss is a little more difficult to spot but once you become aware of it and look for the problem, it is very apparent. To really understand radiation heat loss you should try an experiment. Some cold clear night step outside with your head uncovered. Stand still until you feel slightly cool. Then walk to a nearby overhead protection. This can be a tree, a shed roof or any other non heated overhead barrier. Within minutes you will feel either warmer or a slowing of your heat loss.
In the open your body heat is radiated into space. As soon as something comes between you and space this heat loss is reduced. This is the reason that cloudy nights with freezing temperatures, feel warmer than clear nights with the same indicated temperature. The clouds reduce heat loss through radiation. A hat will reduce radiation heat loss.
Radiation heat loss was recognized by the body long ago and through some act of genetic engineering the head grew lots of hair (some are luckier in this respect than others ;-). Hair grown to full length will cover the head and neck with a good insulating material that maintains its same value even when it is wet. If you have long hair and it can cover your neck, try to arrange it to give your neck maximum protection.
Even breathing fresh air in the cold can kill you. But then, not breathing will certainly kill you. Respiration heat loss occurs as we breathe in cold air, warm it to near body temperature in the nose. throat and lungs , and then exhale it. This loss is increased when we breathe rapidly or when we breathe thorough our mouths.
The heat loss can be reduced by maintaining a constant respiration rate. We can further protect ourselves by breathing through the nose and by covering the mouth and nose with fabric. If the face has been covered by some fabric, the incoming air will be slightly warmed when it meets the resistance to its passage as offered by the fabric. When the air is subsequently exhaled the warm air will heat the fabric and provide a certain amount of preheating for the next breath and so on. Care must be exercised to assure that you do not re-breathe the same air frequently. If your intake of fresh air is reduced beyond a certain level....Well you know….. suffocation.
Perspiration is the method the body uses to cool itself. Wetness due to perspiration, immersion, condensation or as the result of any other action, cools the body rapidly. Perspiration is a common problem for individuals who suddenly find themselves in a survival situation.
As we have seen, panic often forces them to perform strenuous and energy wasting actions such as running. This type of action causes perspiration which then cools by evaporation as the activity diminishes. The best advice to follow is simply "Don't sweat it".
It is also important to realize once again how water loss through perspiration can effect survival potentials. You already realize how much of your ability to do work is destroyed through dehydration. This work can also be work done by the body while it is rewarming itself. Dehydration often accompanies hypothermia. The survival situation may make the adequate intake of fluids very difficult. Even the desire for water is reduced when some people encounter survival stress. Inadequate moisture in the body can increase the tendency for severe shock after a minor injury.
Perspiration wetness cools the body excessively in some conditions and deprives it of its ability to cope with stress. Drink often, try to avoid perspiration, and don't drool onto your clothes.
Heat loss versus heat gain
At first glance it may appear that there are many more ways to lose heat from the body than ways to gain heat. This is almost true, but not quite. What is true is that the heat loss mechanisms exist in nature and we needn't work very hard to experience them. Another fact remains, the heat loss mechanisms can be used as heat gain devices to assist the body in its battle with the cold.
Sit on something warm for heat gain through conduction, stand in warm air for gains through convection. Heat from a fire is mostly radiation, while breathing that hot air from the fire is heat gain through respiration (Possibly heat gain resulting from coughing activity too.) So how does one go about taking advantage of these possibilities?
When we discuss shelter all of these gains will be built into our shelter with various skillful manipulations of natural effects. At that point we will be discussing external heat sources. In the mean time heat loss can be reduced through insulation. The insulation will be devised to defeat the losses we know about and the body most likely will be able to survive on its own resources.
A few simple steps will serve to condense all of this material into survival success in cold conditions. A few preparations will give us the resources to take the steps.
(1) Eat : Whenever you travel in the mountains, eat constantly. Not large heavy meals, just continuous munching
on gorp ( A mix of candies, nuts, raisins, etc.) This will assure you of a full supply of energy should a problem arise. If food is available to you in a survival situation, eat before you go to sleep, you'll sleep warmer.
(2) Sleep : If you have not entered hypothermia, feel cold, but have food and energy, sleep if you can. Should you drop into hypothermia in your sleep, you will wake with the first symptoms, the intense shivering. it'll feel like a giant fist shaking you awake. Most people will awaken if they feel too cold. Death during sleep in the cold is the result of falling to sleep after entering the later stages of hypothermia, or of having trees falling across the sleeping body. Sleep is necessary to rest the body and to help with the repairs that the mind and muscles need. Your decisions after rest are more likely to be accurate and you will have the strength to carry them out.
(3) Drink : Much has been said about this. It is important for you to consume adequate amounts of water to maintain efficiency and strength. The water performs many jobs not the least of which if the removal of chemical poisons that accumulate in the system. If it can be arranged, drink warm liquids. Snow and ice can be consumed but this will add an additional burden to the heating problems faced by the body. Try to melt snow and ice in your trash bag. Avoid alcohol and avoid drugs.
(4) Bivouac early : As soon as you recognize that you have become involved in a survival situation, start making camp. This may be one of the most important things you can do. In the light you can act efficiently to find a good secure shelter and prepare for the night. Do not attempt to push your stressed body across "one more mountain" in hope of finding help. Tomorrow, that can be done in the light. You will need a couple of hours of light to make a secure, warm and comfortable shelter. Do it.
(5) Carry emergency gear : Much is yet to be said about this subject. When we discuss the survival kits you'll begin to realize how simple preparation can be. We already know that the addition of a large trash bag can spell the difference between life and death. Carry one. If you also have the means to make a fire and the knowledge to create a shelter you have a good chance. Your survival situation will have been a fine adventure with plenty of drama and a minimum in of disaster.
Now you know about the number one killer of the woodsy wanderer. "Hypothermia, the killer of the unprepared". It slides into our souls on icy feet, robs us of our minds, incapacitates our bodies and kills us while we sleep. We can stop it with foresight and even banish it with treatment correctly and quickly performed.
Exposure is a serious hazard in the wilderness but there are simple causes and simple cures. Shelter is the only true preventative and this implies preparation. Lets get prepared for cold weather with a little examination of the principles of cold weather shelter.