Hypothermia

“ The same action which blows a fresh wind through the living frame to clear away its impure vapors, also serves to fan its hidden flames, and keep its fuel burning. When the breathing is stopped the fires of the body go out, just as those in a common furnace do, when their air-blasts are arrested, and the body becomes dead cold.
You will remember that when the fresh air is drawn into your lungs as you breathe, it enters a large quantity of little cavities or chambers, which have, all of them, a fine net-work of the supply-pipes stretched out upon their walls ”

“ Indeed, the most effective mechanisms of heat loss involve evaporation of water from the surface of the skin or respiratory pathways (e.g., by sweating, salivation, or polypnea) , which strains the body's precious water resources, whereas heat production (nonshivering or shivering thermogenesis) depletes the body's energy stores. In contrast to autonomic thermoregulation, behavior places no demands on the body's water or energy resources; furthermore, behavioral thermoregulation can compensate for much greater thermal loads. ”

“ As we know, all activity of the body requires an expenditure of energy, so if the body is exposed to a cold damp air for an abnormal length of time it will necessitate an increased expenditure of internal energy to meet the increased demands for heat and thus dissipate forces that should and would, under normal conditions, be utilized in the metabolism of the body. If the heat production is at a minimum in the body, which it may be, due to several factors such as old age, infancy, or dis-ease, this exposure to lowered temperature and high humidity will result in injury to the body. ”

“ The temperature of the atmosphere must, however, be regulated in order that there may not be an abnormal loss of the bodily heat. The bodily heat is being constantly lost to the outside air as follows: 30% by contact with the air, about 43% by radiation and about 27% by exhalation and other losses. We may sit in a room that is warm enough, say 75° F., and yet if we are near a cold wall we will feel chilly. We say we feel the cold coming from the wall, while in reality we feel chilly and cold because the body is losing its heat abnormally to the cold wall by radiation through the air. ”

“ A person [64] who, after exercise that has produced free perspiration, stands in a current of cool air, is apt to take cold. The dryer the atmosphere, the more rapid is the cooling process. The most uncomfortable and oppressive atmospheric condition is that in which the air is heavily laden with moisture and the temperature high. Evaporation from the body is then slow, and the sensation of heat is oppressive.
It is a mistaken notion that clothing keeps the cold out. Its purpose is to keep the heat in, or, in other words, to prevent the rapid radiation of heat. ”

“ The state of asphyxia is relieved, the senses return, the pulse beats at the wrist, and the respiration goes on naturally. The cooling renders the air, unfit before, fitted for the purposes of life.
The effects of temperature upon the respiratory movements are indicated also in those constitutional changes which diminish the production of heat and the consumption of air. Organic affection of the heart or lungs may produce this change, which entails the necessity of a change of climate, or an alteration of temperature artificially, to restore the balance between the air and the animal heat. ”

“ No peril need attend a change from a hot to a cold temperature if the power to evolve heat inherent in the system be entire and active and persistent, not lessened by any of those circumstances which have the effect of weakening it, such as local disease, and fatigue. Cold is dangerous, not especially when the body is hot, but when it is cooling after being heated. At such times taking a large draught of cold water, or cooling the body suddenly some other way might cause death immediately; if not, an inflammation of some internal part of the body might arise. ”

“ The mere application of a chill temperature to the skin is not alone, however, enough to give a cold. This result chiefly comes when the application has been made while the body is in a weakened or exhausted state, and therefore has not the power to resist and overcome the internal disturbance of the even blood-flow. Colds are nearly always caught in consequence of a sudden exposure of the body to a chill, either when it is in a state of exhaustion and fatigue from sustained exertion, or when it has been for some time previously over-heated. ”

“ It must not be overlooked that the air may be fresh and pure, and yet not able to penetrate all parts of the lungs because of superficial and improper breathing.
Relation of Respiration to Body Heat.—The heat of the body is generated by the oxidation of the tissues. The chilliness experienced by persons engaged in sedentary occupations is by no means always caused by the low temperature of the room, as will be proved by the thermometer, but by the close air of the room and superficial respiration, which causes internal overheating with imperfect combustion. ”

“ This is why we are warm. But from some places, as from the skin, the venous blood goes away cooler than the arterial which came, because while journeying through the capillaries of the skin it has given up much of its heat to whatever is touching the skin, and has also lost much heat in turning liquid perspiration into vapour. This is why so long as we are in health we never get hotter than a certain degree of temperature, the so-called blood-heat, 98° Fahr., and why we make warm the clothes which we wear and the bed in which we sleep. ”

“ This fits loosely at the knee, waist, and wrist, enabling the evaporation of constant perspiration to the open air, especially during exercise of any kind. The body is thus kept dry and no energy is lost in heat making.
The usual idea of the amount of clothing necessary to keep the body warm and to prevent freezing in extreme cold is erroneous. It is not so much a question of cold as the degree of dampness on the body surface which is affected by the cold. Nearly every death from freezing is caused by either getting too warm and then wet through perspiration or accidental immersion in water. ”

“ Let me, then, as best I may, consider anew the problem of heat as produced by respiration, and see whether I cannot find out something which has a bearing on the fatal coldness of this fearful disease. It is into the lungs, and no where else, that breathing introduces atmospheric air; and it is there that the oxidation of carbon or animal combustion takes place. Thus must caloric be imparted to the blood in the lungs; and in them is one-fifth of the blood of the system, of which seven-eighths is water.
The nature of heat is to expand all fluids. The blood in the lungs must, therefore, expand ”

“ That is to say, as evaporation always diminishes temperature, so the perspiration, as it passes off in the form of fine vapor, cools the surface. Accordingly, in hot weather this function is much more active, and the cooling influence increases in proportion. When the air is already charged with moisture, and does not readily receive this vapor of the body, the heat of the atmosphere apparently increases, and the discomfort therefrom is relatively greater. ”

“ A common mode of warming is by heated air from a furnace. The chief objection to this is the loss of moisture and of all radiated heat, and the consequent necessity of breathing air which is debilitating, both from its heat and also from being usually deprived of the requisite moisture provided by the Creator in all outdoor air. Another objection is the fact that it is important to health to preserve an equal circulation of the blood, and the greatest impediment to this is a mode of heating which keeps the head in warmer air than the feet. ”

“ Seventy-four below zero by spirit thermometer on the sled.”
“That’s one hundred and six below freezing point—too cold for travelling, eh?”
“Practically suicide,” was the doctor’s verdict. “One exerts himself. He breathes heavily, taking into his lungs the frost itself. It chills his lungs, freezes the edges of the tissues. He gets a dry, hacking cough as the dead tissue sloughs away, and dies the following summer of pneumonia, wondering what it’s all about. I’ll stay in this cabin for a week, unless the thermometer rises at least to fifty below.” ”

“ The danger is, in the first instance, the local perturbation in our heat-economy, which has partly local consequences, but also and chiefly disorders the nerves, acting on the calibre of our blood-vessels, our vaso-motor nerves, which have to regulate the outflow of our heat. When we are in the open, and the air is in more motion than the air of a draught, we speak of wind, etc., but seldom of draught, because the whole air-current flows equally all round us, just as in a well-ventilated room, only with greater velocity. ”

“ On the other hand, if the air is entirely deprived of water vapor, it evaporates moisture from the body, which operation causes an unpleasant sensation. It also takes up a great deal of heat. When the air is saturated, evaporation cannot take place from the body and an unpleasant and depressing effect is produced on the nervous system and the action of the heart. A high temperature in connection with excessive humidity is a frequent source of difficulties with ventilation, and the cause of most complaints as to poor ventilation.
Dust.
A common impurity in the air is dust. ”

“ Cold retards perspiration, and the heat is retained within. The principle of evaporation is illustrated in the manufacture of artificial ice. Men who labor in glass works, iron and steel foundries, and in the engine rooms of large steam vessels are exposed to great heat, yet enjoy as good health as those who are engaged in other occupations. Persons have been known to remain several minutes in an atmosphere heated above the boiling point, without materially increasing the temperature of their own bodies. ”

“ By open fires the lungs get less heat than any other part of us, and so are braced and strengthened; by the hot-air process they get more heat than any other part, because the hottest air rises uppermost about the head, and so is inhaled, making the lungs tender and sensitive to cold on our going out. Put a thermometer at the floor, and another at the ceiling, in a room heated by the hot-air process, and you will find the air at the ceiling from 15° to 45° warmer than at the floor. ”

“ Therefore, an equal bodily temperature should be maintained by exercise, by clothing or by fire.
Exercise warms, invigorates and purifies the body; clothing preserves the warmth the body generates; fire imparts warmth externally. Therefore, to obtain and preserve warmth, exercise and clothing are preferable to fire.
Fire consumes the oxygen of the air, and produces noxious gases. Therefore, the air is less pure in the presence of candles, gas or coal fire, than otherwise, and the deterioration should be repaired by increased ventilation. ”

“ The cold which follows evaporation is caused by a loss of the heat which is required for evaporation, and which passes off with the vapor, as a solution, in the atmosphere; and as heat leaves the body to aid evaporation, it is evident that that body cannot be cooled by the process, below the dew-point at which evaporation ceases. The popular notion that a body may be cooled almost to the freezing-point, in a hot Summer day, by the action of heat alone, is, then, erroneous. ”

“ And it is by the constant modification of these two factors, (1) heat production and (2) heat loss, that the constant temperature of a warm-blooded animal is maintained. Heat is lost to the body through the faeces and urine, respiration, conduction and radiation from the skin, and by evaporation of perspiration. The following are approximately the relative amounts of heat lost through these various channels (different authorities give somewhat different figures) :—faeces and urine about 3, respiration about 20, skin (conduction, radiation and evaporation) about 77. ”

“ The reason of this is, that we cannot feel warm till we have been cold, and vice versâ."
"Our bodies," resumed Fritz, "however much the thermometer descends, never mark less than thirty-five degrees above zero. In winter the skin shrinks, and becomes a bad conductor of heat from without; but, at the same time, does not allow so much gas and vapor to escape from within. In summer, on the contrary, the skin dilates and allows perspiration to form, a process that consumes a considerable amount of latent heat. ”

“ Sugg’s Gas Fires.—During a greater part of the year in this country, the variations in the temperature are so great and sudden, that those persons who have weak throats, or are subject to bronchitis—especially children who have a tendency to croup—find the cold, air of the early mornings a source of great discomfort and even danger. Although by the use of coal fires, with constant attention, the temperature of a bedroom or sick room can be maintained as required during the day, yet at night it is next to impossible to do so. ”

“ Cold air arrests that development by direct paralysis; i.e., by lethargizing and eventually destroying the vitality of the disease-germs. Towards the end of the year a damp, sultry day—the catarrh-weather par excellence—is sometimes followed by a sudden frost, and at such times I have often found that a six-hours' inhalation of pure, cold night-air will free the obstructed air-passages so effectually that on the following morning hardly a slight huskiness of the voice remains to suggest the narrowness of the escape from a two-weeks' respiratory misery. ”

“ The attendant conditions have much influence in determining an attack, thus it is generally held that heat with excess of moisture is the most injurious, yet in Cincinnati, statistics showed a greater number of cases in man when the air was dry. The suppression of perspiration and the arrest of cooling by evaporation in the latter case would tend to a rapid increase of the body temperature, and the condition would be aggravated by the electric tension usually present with the dry air. ”