Water

OLAF MICKELSEN.

NEXT to oxygen, water is the most important factor for survival of man and animals. A person can do without food for 5 weeks or more, but without water he can survive for only a few days.

The exact length of time a person can go without water depends on his rate of water loss. An individual who walks in the desert in the heat of the day may lose water so fast that he dies of dehydration in less than 24 hours. Under more normal circumstances an individual can exist without water for a longer period.

I have read about the case of an 8-year-old girl in Wales, who allegedly was able to grow even though she ate and drank nothing. The publicity given her case in the late 1800's prompted a London physician, who was vacationing in the area, to question its validity. As a result, the parents let the child be observed by nurses, who stood watch around the clock. The girl asked for nothing during the observation period, and no attempt was made to give her anything. On the eighth day, showing signs of extreme dehydration, she died.

The longer an individual goes without water, the greater the number and severity of symptoms he shows.

Weakness, lassitude, thirst, and dryness of the mouth are the first signs of dehydration. Loss of weight and mental confusion set in later. The individual becomes uncooperative and sullen. The cheeks become pale, and the lips are dry and bluish. The skin loses its elasticity. The eyeballs have a sunken appearance. The volume of urine decreases, and its specific gravity rises. At the end, the respiration ceases, even though the pulse and general circulation may be well maintained. The volume of blood is maintained at the expense of the water within the body cells. The central nervous system undergoes the same dehydration as the cells in the remainder of the body and is the first area to show functional changes.

If the dehydration occurs in a very warm place, the person may develop heat cramps, heat exhaustion, or heat stroke before the preceding cycle has run its course.

For heat cramps and heat exhaustion, rest and the administration of salt and water, or water alone, often will restore the patients to normal. Heatstroke requires medical attention, since the patient may die if proper measures are not taken promptly.

About 55 to 65 percent, by weight, of a person's body is water. The exact percentage is related to the amount of fat in the body the more fat, the less water. A 170-pound man with an average amount of body fat contains about 110 pounds of water.

During a football or basketball game, a player may lose as much as 15 pounds most of it water. This water loss must be replenished within a short time, since a normal person can temporarily lose only 5 to 10 percent of his body weight as water before symptoms of dehydration set in.

Our bodies lose water in various ways. The kidneys are the primary way. Some people routinely have small urine volumes. Others have fairly large volumes. The volume reflects the individual's drinking habits and may be altered by changing the volume of fluid he drinks. The volume of urine is reduced when the water lost by other routes is increased unless the intake is increased proportionately.

When the intake of water (both as such and as other fluids) ceases, the urine volume decreases, but there is a lower limit of approximately one-third quart below which the volume in an adult cannot be reduced. As long as metabolic activity continues, even at a very much reduced rate, nitrogenous waste products are formed and require a certain volume of water for their elimination.

Our bodies also lose water through the air we expire. Ordinarily an adult may lose a third of a quart of water a day in this way. Talking and exercise are two obvious activities that increase the loss of water from the respiratory tract.

High altitude is another factor that increases the loss of water in the expired air. The lower concentration of Oxygen in the air at elevations above 8,000 feet produces a compensatory increase in both the rate and depth of breathing. Furthermore, the absolute amount of moisture in the air at high altitudes is low. Since the expired air is Practically saturated with moisture, the amount of water removed from the respiratory passages at high altitudes is greater.

An appreciation of such factors may have helped Sir Edmund Hillary in his conquest of Mount Everest. The records of the earlier Swiss expedition that was unsuccessful in its attempt to scale the peak indicated that each climber consumed less than a pint of water a day for the last 3 days of the climb. The marked water deficit resulting therefrom may have contributed to the extreme fatigue and listlessness of the Swiss climbers during the final stage of the expedition. The British took special precautions to carry extra fuel to melt enough snow and ice to insure each man a daily intake of 5 to 7 pints of water in addition to the water in his food. The British attributed the success of their expedition partly to the increased intake of water.

WE LOSE WATER through our skin by two different mechanisms.

By one of them, we lose the so-called insensible perspiration, which amounts to about a pint a day. The water that collects on a glass surface when we hold the palm of a hand against it is insensible perspiration. The insensible perspiration usually is not detectable, because each area of the skin gives off such a small amount that it evaporates immediately. The cooling produced by the evaporation of the insensible perspiration and the water in our expired air is an important means of maintaining constant body temperature when we are relatively inactive. The heat so lost is related to the amount of energy expended in the absence of visible sweating; it is about one-fourth the caloric expenditure under basal conditions.

Sweating is the other means whereby our bodies lose heat. When our rate of work becomes so great and when the external conditions become so uncomfortable that our bodies begin accumulating heat, we begin to sweat. (We talk about sweat even though some prefer to believe that "horses sweat, men perspire, and women glow.") Sweat, unlike insensible perspiration, contains sodium chloride, urea, and tiny amounts of calcium, potassium, and some water-soluble vitamins.

The sodium chloride has received a great deal of attention. Many persons believe that extra salt must be consumed during warm weather or when their work exposes them to hot temperatures (blast-furnace workers, cooks, and bakers, for example). They believe extra salt is necessary to replace that lost in the sweat. Actually, an ordinary American diet provides a salt intake of about 10 grams a day, which is enough to permit an adult to withstand even the most vigorous sweating as long as his water intake is maintained.

The water lost in sweat should be replaced as soon as possible to forestall fatigue, which is one of the earliest symptoms shown by individuals who are short of water. To maintain your work efficiency during hot weather, you must consume water throughout the period of exposure to heat.

The evaporation of sweat is an important means of maintaining body temperature in hot climates. The evaporation of 1 quart of sweat dissipates 580 Calories of heat. This amount of energy expended in an hour would represent very heavy work.