Essentials of Wilderness Survival

Chapter 41 Essentials of Wilderness Survival



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This chapter discusses the general principles of wilderness survival, particularly in temperate and moderately cold (i.e., nonpolar) environments such as the mountains of the American West. For additional information, especially about other environments, please refer to Chapter 1 for high-altitude medicine, Chapter 9 for polar medicine, Chapter 43 for jungle survival, Chapter 44 for desert survival, Chapter 71 for how to live off the land, Chapter 96 for wilderness navigation techniques, and Chapter 112 for certain aspects of environmental changes (e.g., global warming).


According to Webster’s College Dictionary, the word survive means to “continue to function or manage in spite of some adverse circumstance or hardship,” and it implies the presence of conditions that make this more difficult than usual. These conditions may—and frequently do—include a lack of oxygen, food, or water; the presence of rain, snow, high winds, or temperature extremes without shelter; the complicating presence of illnesses or injuries; and the necessity to rely completely on the physical, mental, and material resources that are immediately at hand. Physicians who participate in wilderness recreation or who treat such participants need to be aware of the physical, physiologic, and psychological hazards of environmental stress and how related deleterious effects can be prevented and treated in themselves and their patients.


Increased leisure time and growing interest in outdoor activities place more people into settings in which survival situations may develop. The increasing use of all-terrain vehicles and snowmobiles has made it easier to get lost or stranded far from help. In addition, the rise in sedentary lifestyles with inattention to healthy diets, decreased emphasis on physical conditioning, and increasing prevalence of obesity have led to decreased fitness in developed nations, particularly the United States. With modern communications and tactics (e.g., the use of combined helicopter and ground teams), search and rescue operations have become more efficient. At the same time, electronic devices such as cellular and satellite phones, global positioning system (GPS) locators, emergency locater transmitters for aircraft, and personal locator beacons have made it easier to get assistance, but these are accompanied by increased risk taking, a false sense of security, a decrease in a healthy respect for wilderness, a neglect of survival training, a failure to carry survival equipment, and the less-effective use of simple nonelectronic tools such as maps and compasses. An especially egregious practice is the “Yuppie 911,” when a personal locator beacon that sends a message to a satellite is used for a nonemergency situation. In some cases, carrying such equipment tempts wilderness travelers to take chances that common sense would otherwise prevent. According to the Billings Gazette, in one recent episode, an inexperienced party made three calls in three days from the Grand Canyon, thus “mobilizing helicopters for dangerous, lifesaving rescues inside the steep canyon walls. What was that emergency? The water they had found to quench their thirst ‘tasted salty.’ ”


Societal “progress,” then, has made it easier to get assistance when there is trouble, but it is now also easier to get into trouble. This chapter’s main thrust is prevention and successful initial definitive management of such trouble. By paying heed to the recommendations discussed here, the reader will be more apt not only to live through the stress of a survival emergency but also perhaps to do so in relative comfort.


A recent episode in Montana illustrates the types of problems that wilderness travelers such as hunters can experience, and emphasizes both the penalties for risk taking and the role of technology in the softening of these penalties. Glenn Eschenko, who was 51 years old, ran a bowling alley and supper club in Big Timber, Montana. A longtime hunter and mule owner, he had returned to the same camp near Anderson Mountain in the Absaroka-Beartooth Wilderness for 20 years. He packed in enough gear to spend a week hunting elk next to the border of Yellowstone National Park. In 2005, he had been hunting for 6 days with four friends. They had harvested a six-point bull elk when the weather started to turn nasty on Saturday, September 17. After four of them had lunch, two of them (Eschenko and Chad Cochran) saddled up to look for the fifth hunter (Courtney Ayers), who had not returned.


Eschenko was riding one of his older mule colts when he came around a corner in the rain and saw Ayers up ahead. Ayers was riding down a mountain toward him, wearing a yellow rain slicker. The slicker startled Eschenko’s mule, who whirled and started bucking, throwing his rider after about five jumps. Eschenko was thrown down an embankment, sliding on a skiff of snow on the grass, hitting a rock, and then sliding on his belly farther downhill before crashing into a boulder.


Eschenko was able to stagger to his feet, but the wind was knocked out of him, and he could feel loose and moving broken ribs on his left side. His friends loaded him onto another mule and got him back to camp, but he could not move because of his dyspnea.


Cochran had a cell phone and called 9-1-1. A helicopter was dispatched from St. Vincent’s Hospital in Billings, about 160 km (100 miles) away, but it was unable to land because of bad weather. Cochran rode to a nearby outfitters camp and asked a nurse for advice. She told him that if Eschenko was still alive when he got back, then the injured hunter would probably survive.


The party spent a cold night by a roaring campfire; Eschenko was still alive the next morning. A helicopter from Idaho was set to make a rescue run, but again the weather was too severe. Finally, a helicopter from Mammoth, Wyoming, was dispatched; the camp was found as a result of the pilot’s use of GPS coordinates that the hunters had called in, and the aircraft was able to land at a mountain meadow above camp and drop off two emergency medical technicians. Fearful of getting fogged in, the craft departed down the mountain around 8:30 AM.


The emergency medical technicians noted extreme tenderness in Eschenko’s left upper quadrant and felt that his spleen was probably ruptured. Because extreme pain limited Eschenko’s movement and ability to walk, his companions managed to transport him by mule 0.8 km (0.5 miles) to a place where the helicopter could land safely. Eschenko was flown back to Mammoth, where an ambulance was waiting to take him to Livingston Memorial Hospital in Montana. A doctor told Eschenko that he had cheated death because his spleen was “pulverized” although not freely bleeding. Once he was out of the hospital, Eschenko sold the mule that had bucked him. He then planned to show his other mules yellow raincoats to get them used to the sight. He also said that he had acquired an appreciation for cell phones and GPS receivers.


The exact type of environmental stress depends on the type, location, and duration of the wilderness experience. Cross-country skiers, winter mountaineers, and winter campers may be exposed to extremes of cold and storm. Expeditionary mountaineers may explore regions in which winter exists year round and where ambient oxygen is low. Desert or tropical travelers may be exposed to extremes of heat and humidity. Passengers in aircraft, seacraft, or land vehicles may be stranded in almost any type of environment.


Requirements for survival, which are discussed in detail later in this chapter, are similar whether the subject becomes lost with few resources during a simple day hike or whether injury occurs or severe environmental conditions develop during a well-planned wilderness expedition. Although traveling alone in the wilderness is universally condemned, one must always assume that he or she may be alone and possibly injured when in a survival scenario. Therefore, emergency equipment must be familiar, sturdy, uncomplicated, easy to assemble, and—most importantly—available immediately. Necessary skills cannot be learned on the job but must be anticipated, acquired and practiced beforehand so that essential tasks can be accomplished with minimal delay and effort should an emergency arise. Although improvisation and the ability to live off the land are important, anticipation, prevention, and especially preplanning and carrying emergency equipment are vital. Consider examples taken from polar exploration: Roald Amundsen’s style of thorough preparation and the use of familiar equipment should be emulated, whereas Robert Scott’s careless, arbitrary, and stubborn approach should be rejected. Both of these explorers had extensive polar experience, but Scott elected to use European clothing rather than Eskimo furs and unproved motor sledges and ponies rather than Eskimo dogs. He relied excessively on sled hauling by men on foot, rejected the use of skis, failed to establish enough supply depots for his return, and died of cold, exhaustion, and starvation on the way back from the South Pole. Amundsen, who used Eskimo clothing, well-tested Greenland sled dogs, and experienced skiers, won the race to the South Pole and made it back alive.


The outcome of an encounter that involves severe environmental stress varies with the stressed person’s resources and the type, magnitude, and duration of the stress. These resources include the state of acclimatization; physical integrity (particularly conditioning and the presence of illness or injury); experience; equipment on hand plus the ability to improvise intelligently; and such intangibles as good judgment and “backcountry common sense.” A common judgment error is to insist on traveling during a storm or other stressful environmental situation, when more prudent persons would stay put in a comfortable bivouac. Excuses for this include wanting to reach a predetermined (but not essential) goal on time so that others will not worry. Recall the old adage, which has been attributed to Will Rogers, that “good judgment comes from experience; experience comes from bad judgment.” To this, we should add, “…provided that you survive the bad judgment.” The most important resource, however, may be the will to survive. This may be inbred in some persons, can be established through training and experience in many, and is impossible to acquire in a few. With a strong will to survive, some persons have withstood incredible hardships. Without such will, the best training and resources may be useless.


Although it is based on science, the study and practice of survival is more a craft or learned skill than an exact science. The recommendations in this chapter are based on the opinions of survival experts, research, analysis of actual survival situations, and personal experience. General principles are emphasized, but “tricks of the trade,” which are usually acquired through experience, may hold the key to life or death. Unfortunately, much of the lay literature emphasizes tales of misfortune, hazardous adventures, and mindless bravado in the face of unnecessary hardships that are brought on by the errors of the participants, whereas great deeds go unrecorded or forgotten because the experience and competence of the adventurers kept catastrophic “newsworthy” experiences to a minimum. In the words of Corneille, “To vanquish without risk is to triumph without glory.”


Travelers should always plan for the unusual and unexpected. Tools include familiarity with weather forecasts, strategizing worst-case scenarios, carrying emergency items, avoiding solo travel, and leaving notice of the projected route and the expected time of return. With good planning, deteriorating weather or an injury-forced bivouac become more of an inconvenience than a life-threatening ordeal. However, chance always plays a part in survival. Serious but unforeseen or unavoidable hazards can occur, or environmental stresses can become so severe that survival is impossible regardless of preparations. Anyone who ventures into the wilderness must accept the possibility—however remote—of death or serious injury.


For survival, the body requires a constant supply of oxygen; a core temperature that is regulated within relatively narrow limits (about 24° to 42° C [75° to 107° F]); water and food; and self-confidence, faith, and the will to live. For comfort and optimum performance, however, the body temperature must be close to normal, and the body must be rested, well nourished, in top physical condition, and free from disease and injury. The most immediate of these latter requirements are the maintenance of body integrity (through accident prevention) and the regulation of body temperature. Dehydration, starvation, and exhaustion make temperature maintenance more difficult and interfere with the rational thought and agility required to prevent accidents. Insufficient oxygen becomes a contributing factor at extreme altitudes or in such mishaps as suffocation caused by avalanche burial or carbon monoxide poisoning from cooking in an unventilated shelter. Abundant food and water are of little value to a hypothermic person with insufficient clothing and shelter or to the victim of heat stroke, although a lack of food and water will eventually weaken and kill an otherwise healthy individual. A lack of self-confidence, faith, and the will to live may cause an attitude of panic and defeatism that prevents a person from taking timely survival actions such as conserving energy, preparing shelter, or lighting a fire. Poor physical conditioning or the presence of illness or injury may interfere with the body’s ability to produce heat by shivering or to lose heat by sweating and increasing skin perfusion; this can hamper wood gathering, shelter building, and other necessary tasks.


The most important organ for survival is the human brain, because voluntary actions such as preparedness, regulation of energy expenditure, adjustment of clothing, and provision of shelter are more important than are involuntary mechanisms of adaptation to environmental stress.



Oxygen


As a human ascends from sea level, the body is subjected to increasing cold, decreasing oxygen, increasing solar radiation, and decreasing atmospheric pressure. For every 305 m (1000 feet) of altitude gain, ambient temperature drops by about 2.2° C (4° F), barometric pressure drops by about 20 mm Hg (27 millibars or roughly 0.1 millibar drop per meter of altitude gain), and the amount of ultraviolet radiation increases by about 5%. The percentage of oxygen in the atmosphere remains constant, but partial pressure of oxygen diminishes with altitude so that, at 3077 m (10,000 feet), it is only two-thirds of that at sea level; at 5488 m (18,000 feet), it is only one-half of that at sea level.


During acute exposure to high altitude, effects of hypoxia can initially cause fatigue, weakness, headache, anorexia, nausea, vomiting, dyspnea on exertion, insomnia, and Cheyne-Stokes respirations. These symptoms are probably present to some degree in everyone who goes rapidly from sea level to 2462 m (8000 feet) or above. The clinical effects of hypoxia are often difficult to distinguish from those of cold, high winds, dehydration, and exhaustion. Serious degrees of acute mountain sickness are unusual below 3692 to 4308 m (12,000 to 14,000 feet), but they have been reported in trekkers as low as 2308 m (7500 feet). As noted during one author’s experience as a periodic summer physician in Yellowstone National Park, mild acute mountain sickness is occasionally seen in visitors at just over 1829 m (6000 feet) at the north entrance. At any height, oxygen in ambient air may be prevented from reaching the cellular level because of interruption of normal transport pathways, generally by illness or injury. Carbon monoxide poisoning is probably a greater hazard than is generally appreciated. Many famous polar explorers, including Byrd, Andree, and Stefannson, were killed by or had narrow escapes from the toxic effects of stoves operated in tightly enclosed spaces.



Regulation of Body Temperature


Humans are considered homeotherms because, as warm-blooded animals, they maintain a body temperature that varies within very narrow limits despite changes in environmental temperature. In poikilotherms, which are cold-blooded animals, body temperature varies with the temperature of the environment. Homeothermy is necessary to support the enzyme systems of the human body, which function best at 37° to 37.5° C (98.6° to 100° F). The human body can be viewed as a heat-generating and heat-dissipating machine, where internal temperature is the net result of opposing mechanisms that tend to increase or decrease body heat production, increase or decrease body heat loss, and increase or decrease addition of heat from the outside. With use of these mechanisms, internal body temperature can usually be regulated successfully, despite ambient temperatures that vary by more than 55° C (100° F) from the coldest to the hottest seasons in temperate climates.


Basal body heat production is about 50 kcal/m2/hr. This can be increased by muscular activity (both involuntary [shivering] and voluntary), eating, inflammation and infection (fever), and in response to cold exposure. Shivering can increase heat production up to five times the basal rate, and vigorous exercise can increase it up to 10 times. Cold exposure increases hunger; secretion of epinephrine, norepinephrine, and thyroxin; and semiconscious activity, such as foot stamping and dancing in place. Eating provides both needed calories and the temporary increase in basal metabolic rate that occurs during digestion alone; this is specific dynamic action (SDA). The SDA of protein is five to seven times higher than that of fat and carbohydrates, and it lasts longer. However, onset of the SDA is much faster with carbohydrates than with protein or fat. Therefore, the person who is cold inside a sleeping bag at bedtime should eat carbohydrates for quicker warming and protein to stay warm all night. In hot weather, body heat production can be decreased by slowing muscular activity and avoiding foods with a high SDA.


In cold weather, heat can be added to the body by exposure to a fire or another heat source (e.g., sunlight) and by ingesting hot food and drink. In hot weather, external heat addition can be decreased by staying in the shade, wearing clothing that blocks the sun’s rays, and avoiding hot objects and hot food and drink.


The body loses heat to the environment by conduction, convection, evaporation, radiation, and respiration; it may gain heat from the environment by the same mechanisms (except for evaporation). The relative importance of these mechanisms depends on temperature, humidity, wind velocity, cloud cover, insulation, contact with hot or cold objects, sweating, and muscular exercise. With a resting body in still air at 21° C (70° F), radiation, conduction, and convection account for about 70% of total heat loss; evaporation accounts for about 27%; and urination, defecation, and respiration account for only 3%. During work, however, evaporation may account for up to 85% of heat loss.


It is useful to think of the body as being composed of a core (i.e., the heart, lungs, liver, adrenal glands, central nervous system, and other vital organs) and a shell (i.e., the skin, muscles, and extremities). Most of the physiologic adjustments in response to cold or heat exposure occur in the shell. These adjustments are intended to maintain a relatively constant core temperature; in below-freezing weather, these adjustments may predispose parts of the shell to frostbite and other types of localized cold injury.


The importance of avoiding travel and seeking shelter during storms and extreme cold cannot be overemphasized. The additive chilling effect of wind when added to cold is impressive. Wind-chill charts (Figure 41-1) show the relationship between actual temperature, wind velocity, and “effective” temperature at the body surface. The term wind chill refers to the rate of cooling; the actual temperature reached is no lower than it would be if wind were absent (unless evaporation of liquid is occurring at the body surface). The increase in heat loss as the wind rises is not linear; rather, it is more proportional to the square root of the wind speed.



At moderate ambient temperatures, the body’s core temperature is kept stable by constant small adjustments in metabolic rate, muscular activity, sweating, and skin circulation. When the body is chilled, automatic and semiautomatic mechanisms increase internal heat production by slightly increasing metabolic rate, shivering, and semiconscious activities (e.g., foot stamping), and they reduce heat loss by diminishing sweat production and shell circulation. The person has a strong urge to curl up into a ball, thereby reducing the body’s surface area. At the same time, the brain tells the body to decrease heat loss by adding insulation and wind protection, seeking shelter, and increasing heat gain by increasing muscular activity, building a fire, seeking sunlight, and eating.


When the body overheats, these actions are reversed. The body increases heat loss by increasing circulation to the skin and extremities and by increasing sweating. These mechanisms require more water, which stimulates the thirst response. Heat production is decreased as a result of a feeling of sluggishness and languor, which leads to reduction in physical activity and in the amount of heat produced by the muscles. The brain tells the body to decrease heat gain and to increase heat loss by providing shelter from the sun, removing clothing, and fanning itself.



Cold Weather Survival


Body temperature in a cold environment is maintained by decreasing body heat loss, increasing internal body heat production, or adding heat from the outside. The most efficient of these methods is the conservation of body heat by decreasing heat loss, generally with the use of clothing and shelter.



Decreasing Body Heat Loss


Heat loss from conduction and convection can be prevented by interposing substances of low thermal conductivity, such as clothing made of insulating materials, between the body and the outside air. Clothing creates a microclimate of warmed, still air next to the skin surface. Clothing’s value depends on how well it traps air, the thickness of the air layer, and whether these qualities are reduced by wetting (Table 41-1). Traditional insulating materials are wool, down, foam, and older synthetics such as Orlon, Dacron, and polyester. Wool retains warmth when wet because of a moderately low wicking action and its ability to suspend water vapor within its fibers without affecting its low thermal conductance. It can absorb a considerable amount of water without feeling wet, but is heavier than synthetics, “itchy,” and more difficult to dry. However, its toughness and durability make it a good choice for garments that are subject to hard wear, such as trousers, mittens, and socks. Cotton, particularly denim and corduroy, is a poor insulator. It dries slowly because of its low evaporative ability; high thermal conductance is further increased by wetting. Cotton has no place in the backcountry in cold weather.



Orlon, Dacron, acrylic, and polyester were developed to duplicate wool’s properties without wool’s high cost and other perceived drawbacks. They traditionally have been used for hats, shirts, sweaters, and long underwear. They are almost as warm and not as itchy as wool, and evaporate moisture better. A number of newer fabrics are woven from fibers that have lower thermal conductance, greater insulating ability, and better wicking action than do traditional fibers. Examples include polypropylene and treated polyesters such as Capilene, Thermax, and ThermaStat. Polyester is also made into pile and fleece; these are light, dry easily, trap air well, and stay warm when wet because the fibers do not absorb water. Examples include Polartec, Borglite, Polarplus, and Synchilla. Fibers used as fillers in quilted garments, such as parkas, include hollow synthetics, such as Hollofil II and Quallofil, which were designed on the basis of the principles of reindeer hair. Microfibers that provide good insulating ability with less bulk include Thinsulate, Thermoloft, and Thermolite. One of the newer fibers, Microloft, is supposed to be warmer than down of the same weight. New synthetics come on the market frequently, so one should consult trade journals and “gear” issues of outdoor magazines.


The layering principle of clothing is effective for preventing both chilling and overheating. Multiple layers of clothing provide multiple layers of microclimate. Layers are added as necessary to prevent chilling or subtracted to prevent overheating that would cause perspiring. Because water conducts heat 25 to 32 times faster than air at the same temperature, clothing that is wet with perspiration or water may cause rapid heat loss from conduction and evaporation. The need to add or subtract layers should be anticipated before either chilling or heavy perspiring occurs.


Clothing should be easily adjustable, sweaters should be closeable from the waist to the neck with a sturdy zipper, and outer layers should be cut full enough to allow for the expansion of inner layers to their full thicknesses. Zippers in the axillary, lateral chest, and lateral thigh areas are useful for ventilation.


Loss of heat from convection can be prevented by wearing windproof outer garments. Typical examples include a parka with a hood and a pair of windproof pants (regular or bib style) or ski warm-up pants.


Loss of heat from infrared radiation can also be prevented by insulation and emphasizing the proper covering of body parts with a large surface area–to–volume ratio. The uncovered head can dissipate up to 70% of body heat production at an ambient temperature of −16° C (5° F), partly because the body does not reduce blood supply to the head and neck in cold weather as it does to the extremities. High heat loss through radiation during cold nights can be decreased by sleeping in a tent or under a tarpaulin instead of out in the open.


Coverage for the head, ears, hands, and feet should not restrict circulation. Developed initially for skiers, a tubular neck gaiter can be pulled up over the back of the head to form a hood or up over the lower face to form a mask. In addition to head and neck protection, this device also blocks some of the heat that would otherwise be lost by the bellows action of clothing that is caused by body motion.


Heat loss from the respiratory tract can be diminished by avoiding overexertion and overheating that occur with excessively heavy breathing. When it is extremely cold, inspired air can be warmed by pulling the parka hood out in front of the face to form a “frost tunnel.”


Heat loss from conduction occurs as a result of direct contact with a colder object. Sitting on a pack, a foam pad, a log, or another object of lower heat conductivity is preferable to sitting in the snow or on a cold rock. At low temperatures, bare skin freezes to metal; avoid this by wearing light gloves when handling metal objects. Gasoline and other liquids with freezing points lower than that of water can cause frostbite if they are accidentally poured on the skin at low temperatures. During bivouacs in snow shelters, avoid contact with the snow by sitting on a foam pad or backpack or by improvising a mattress of evergreen boughs, grass, or dry leaves. In cold or windy weather, an injured person needs windproof insulating material under as well as over and around the body.


Heat loss from conduction and evaporation can be lessened by avoiding wetting and by changing to dry clothes or drying out quickly when wet. Ideally, outer clothing should be windproof, and it should not collect snow. It should shed water but not be waterproof, because waterproof garments prevent the evaporation of sweat; laminated fabrics such as Gore-Tex and its relatives are designed for this purpose.



Dressing for Cold Weather


Anyone who ventures outdoors in cold weather should have enough clothing of the proper kind, either on the body or in the backpack, for the most extreme environmental conditions that are likely to be experienced. Although building fires, carrying emergency shelters, and improvising survival shelters are discussed at length later in this chapter, the process of dressing for cold weather should be approached with the idea that clothing may become the only shelter and endogenous heat production the only heat available. Clothing and other types of insulating materials should be selected with the idea that they need to keep the body warm and dry even during periods of inactivity.




Second Layer







Third Layer



Parka


The parka can be a standard ski or mountain parka filled with down, Dacron, Quallofil, Thinsulate, or another lofting material. A more versatile combination is two separate garments: a pile jacket plus a water-resistant shell. For snow camping, a pile jacket with a thin outer cover of nylon (i.e., three-season, squall, or warm-up jacket) may be preferred, because, unlike an uncovered pile jacket, it does not collect snow when it is worn without the shell. The shell should have a hood with a drawstring, a two-way zipper with an overlying weather flap closed with full-length Velcro (in case of zipper failure, very cold hands, or upper extremity injury), a cloth flap to protect the chin from the metal zipper pull, armpit or lateral chest zippers for ventilation, and at least four outer pockets plus one or two inside pockets to contain frequently needed items (e.g., gloves, compass, map, sunglasses, neck gaiter). Outer pockets should be located where they can be reached while wearing a backpack with a fastened waist belt. The shell should be fingertip length unless bibs are worn. Zippers should have extra-long tabs added to facilitate closure with cold or mittened hands.


Pockets with horizontal openings may close with Velcro, but those with vertical openings should close with zippers. Because the parka is anchored by the shoulders, when using one hand, it is generally easier to pull a vertical zipper down rather than up. In some brands of parkas, vertical zippers are pulled down to close the pockets; in other brands, they are pulled up. The authors prefer the former type: the danger of losing pocket contents as a result of difficulty with closing a zipper is worse than any perceived delay caused by difficulty with opening a zipper.


For ventilation, there should be zippered openings at the armpits. These should be large enough so that the parka can be converted into a vest-like garment during warm conditions by inserting the wearer’s arms through the openings and tucking the sleeves inside the parka. Because these zippers usually perform more easily when they are pulled from the distal to the proximal direction, this direction should close them; increasing wind protection is usually more urgent than decreasing it (i.e., freezing is more dangerous than sweating).




Hand gear


Mittens and gloves provide hand protection from trauma and cold. Because survival depends to some extent on normal hand dexterity, gloves or mittens should be available to protect the hands from cuts, bruises, blisters, and possible resulting infections. In temperate weather, these can be light and unlined leather gloves.


One of the more serious and still unsolved cold weather problems is how to keep fingers warm while leaving them sufficiently unhampered to do work. Mittens are warmer than gloves, because fingers that touch each other warm each other. However, even thin mittens do not allow for delicate finger movements. An important part of the cold-finger solution is to prevent core cooling and compensatory extremity vasoconstriction by addressing core temperature stabilization through exercise, eating, and wearing enough layers on the trunk.


A common method is to wear a pair of thin gloves of polypropylene, silk, thin wool, or polyester/Lycra inside a wool or pile mitten covered with a windproof and water-resistant shell. For delicate finger work, the gloved hand is removed from the mitten, the work done as fast as possible, and then the hand returned to the mitten. However, because insulating materials insulate in both directions, when inside a warm mitten, cold fingers wearing gloves will not rewarm as fast as cold, bare fingers. Therefore, another solution is to use bare fingers, which will perform faster than gloved fingers, work as fast as possible, and then return them to warm mittens periodically until the task is done. However, this is not practical when working with metal in very cold weather. Another approach is to keep a pair of gloves warm in a pocket and put them on after removing the hands from mittens. Polyester/Lycra gloves are easier to don than are many other types of thin gloves.


Excellent three-layer mitten sets include windproof shells with leather palms and two sets of removable pile mittens, at least one of which is fastened to the inner shell with Velcro. Another good system is a thin glove liner inside a heavy wool mitten (e.g., Dachstein, rag wool, wool/polypropylene) inside a Gore-Tex shell.


An option that provides more finger dexterity in moderately cold conditions is a polypropylene glove liner inside a fingerless wool glove inside a shell. A newer combination is a fingerless wool glove inside a wool mitten that has a horizontal slit in the distal palm (i.e., Cordova’s rag wool convertible gloves). The distal tip of the mitten can be folded backward dorsally and secured with a Velcro patch, thereby allowing the hand that is covered with the fingerless wool glove to be exposed through the slit. However, more layers and increasing complexity mean more difficulty doing delicate hand tasks.


Shells should have easily accessible nose warmers of pile or mouton on their backs, they should be long enough to cover the wrists, and they should have palms of soft leather or sticky fabric for securely holding ice axes and ski poles.





Shelter







Tarpaulins


Sheets of Visqueen plastic, painters’ drop cloths, large pieces of canvas, or other similar materials can be used to erect a wide variety of effective survival shelters. “Blue crinkly” plastic tarps made of a laminated polyethylene weave are readily available and inexpensive; they can be purchased from most hardware stores, they come in a variety of sizes, and have grommets inserted along the edges. A tarp, no smaller than 2.4 × 3 m (8 × 10 feet), is needed to protect an adult. Tarps of this size weigh about 0.7 kg (26 oz) and roll up into a tube that is 15 cm (6 inches) in diameter by 30 cm (12 inches) long, which is convenient to carry tied to the outside of a daypack or a fanny pack. To save valuable time in a survival situation, tie 3 m (10 feet) of parachute cord to each corner grommet ahead of time.


Tarps can be erected in a number of shelter styles, depending on weather conditions (Figure 41-3). To erect a lean-to shelter, first select a line that is long enough to stretch between two trees that are far enough apart for the tarp to be stretched tight. With the use of a timber hitch, tie off one end of the line to one of the trees at about chest height. Then, rather than passing the line itself through the grommet eyes, insert a small loop of the line through the first grommet eye, and secure the loop with a short stick that is thrust through it on the opposite side (Figure 41-3, B). Repeat this process for each grommet, stretching the tarp tight each time. After the tarp is attached to the line, tie off the other end of the line to the second tree, with the line stretched as tightly as possible. The lower edge of the tarp is then pegged to the ground or anchored with large stones or a length of log. When making pegs, select a length of wood that is 3.8 to 5 cm (1.5 to 2 inches) in diameter and that is twice as long as needed. With a saw, make one 45-degree cut at the midpoint of the stick. In this way, one cut produces two pegs, both of which are sharp enough to be driven into the ground by pounding their blunt ends with the back of an ax head or a large rock. Fill in the sides of the lean-to with vegetation.



If a fire will be built in front of the lean-to, the front opening should be parallel to the prevailing wind so that the smoke will be carried away from the shelter. If not, the back edge of the lean-to should point to the prevailing wind.


To erect a pup-tent type of shelter (Figure 41-3, C), tie a line between two trees, drape the tarp over it, and peg down the sides. Block the ends with vegetation or personal equipment.


A lean-to with an eave (Figure 41-3, D) gives more protection from rain and snow than does one without an eave. Instead of attaching the long edge of the tarp to the line between the two trees, drape the tarp over the line so that several feet are on the other side, and then tie the two corners to pegs for a down-sloping eave.


A triangular tarp shelter can be erected rapidly and provides good protection (Figure 41-3, E). It requires three pegs and an anchor point on a tree.




Winter and Cold Weather Emergency Shelters


Everyone who spends time in the winter wilderness should practice the construction of several types of emergency survival shelters before such shelters may be needed. The functions of a shelter are to provide an extension of the microclimate of still, warm air that is furnished by clothing; to contain the heat generated by the body, a fire, or other heat source; and to protect the individual from snow, rain, and wind. A properly designed shelter should allow easy and rapid construction with simple tools and should provide good protection from wind, rain, and snowfall. The type and size of shelter depend on the presence or absence of snow and its depth; on the natural features of the landscape, including the availability of natural building and insulating materials; and on whether firewood or a stove and fuel are available. If external heat cannot be provided, a shelter must be small and windproof to preserve body heat.


If possible, a shelter should be constructed in the timber to provide protection from the wind and access to firewood. Generally shelters partway up the side of a ridge are warmer than those in a valley, because cold air tends to collect in valleys and basins during the night. Exposed windy ridges above the timberline are cold. Areas that are exposed to flooding (e.g., drainages, dry riverbeds), rockfalls, cornice falls, or avalanches or that are under dead trees or limbs should be avoided. If open water is available, the camp may be located nearby, although in nonsurvival conditions camps should be at least 61 m (200 feet) from bodies of water. To avoid drifting snow, tents and shelters should be located with the entrance parallel to the prevailing wind.


Snow is a good insulator (Table 41-2). Its heat conductivity is 1/10,000 that of copper, and its insulating ability superior to wool felt, so snow shelters may be warmer than other types of constructed shelters as long as the inhabitants remain dry. Contact with the snow or cold ground is avoided by sitting on a foam pad, dry leaves, grass, a backpack, or (in survival conditions only) a bed of evergreen boughs.


TABLE 41-2 Thermal Conductivity of Various Substances



































































Substance Conductivity* Temperature Measured (° C)
Air 0.006 0
Down 0.01 20
Polyester (hollow) 0.016
Polyester (solid) 0.019
Snow (old) 0.115 0
Cork 0.128 30
Sawdust 0.14 30
Wool felt 0.149 40
Cardboard 0.5 20
Wood 0.8 20
Dry sand 0.93 20
Water 1.4 12
Brick 1.5 20
Concrete 2.2 20
Ice 5.7 0

* Conductivity is the quantity of heat in gram calories transmitted per second through a plate of material that is 1 cm thick and 1 cm2 in area when the temperature difference between the sides of the plate is 1° C.





Snow Shelters


A snow trench is the easiest and quickest survival snow shelter and the one that is least likely to make the diggers wet. It can be dug in most areas that are flat or on slight to moderate inclines as long as the snow is 0.9 m (3 feet) or deeper or can be piled to that depth. A 1.2 × 1.8-m (4 × 6-feet) trench can be dug in 20 minutes, with one end roofed over with a tarp or boughs and a fire built at the opposite end (Figure 41-7). Again, adjustments may need to be made to avoid excessive smoke exposure, which can be prevented to some extent by setting the long axis of the trench at a right angle to the apparent wind direction.



If a large (2.4 × 3 m [8 × 10 feet]) tarp and a stove are available, a trench can be dug that is as comfortable as a snow cave; this will hold two or three people. The object is to keep the maximal amount of snow around and over the trench. The trench is dug as narrow as possible at the surface while still providing sufficient room to shovel; a suitable size for the top is 1.2 m (4 feet) wide by 2.4 m (8 feet) long. It is undercut at the back and sides so that the bottom is 1.8 to 2.1 m (6 to 7 feet) wide by 2.7 to 3 m (9 to 10 feet) long (Figure 41-8). A narrow entrance helps to contain heat and can be closed with a small plastic sheet or a pack. Four or more skis or thick limbs are laid from side to side over the top of the trench, with ski poles or branches interwoven at right angles. A tarp is then laid on top of these and the snow piled around its edges to hold it down. In very cold weather, the entire tarp can be covered by a layer of snow; at least 20 cm (8 inches) is needed for proper insulation. When the entrance is closed, a small stove and the occupants’ body heat will raise the interior temperature to −4° to −1° C (25° to 30° F). Higher temperatures should be avoided so that clothing and bedding will not become wet from melting snow.


Sep 7, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Essentials of Wilderness Survival

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