Exposure to the Elements
Exposure to the Elements
Although humans are among the most adaptable of the earth's creatures with one of the broadest territories of settlement, their ability to survive extreme temperatures is limited. Death can occur by exposure to extreme heat or cold. A person who falls through the ice into water will typically die within twenty to thirty minutes because of heart standstill or heart fibrillation. By then, his or her internal or core body temperature will have fallen to approximately 77 degrees Fahrenheit. Often death is a combination of stresses to the body such as hypothermia and starvation as in the case of the Donner party, the ill-fated group of emigrants that was caught in the Sierra Nevada Mountains during the winter of 1846. The decrease in core body temperature is compensated for by shivering, constriction of surface blood vessels to direct the blood to internal organs, and behavioral actions such as increasing voluntary exercise or putting on more clothes. As hypothermia sets in the rate of all metabolic processes slows down, leading to loss of judgment, apathy, disorientation, and lethargy. Breathing becomes slower and weaker, the heart slows, and disturbances in cardiac rhythm occur, leading to death. Many symptoms of hypothermia were evident in the oral and written accounts of the Donner party, adding to the inability to supplement their rapidly decreasing food supply.
The limits for hot air temperature that one can stand depend on whether the air is wet or dry. The core temperature of a nude body can remain within normal range (97 to 99 degrees Fahrenheit) for hours when exposed to dry air ranging from 55 to 130 degrees Fahrenheit. However, if the humidity of the air approaches 100 percent or if the person is submerged in water, the core temperature will rise whenever the environmental temperature rises above 94 degrees Fahrenheit. The body responds to heat stress by sweating, dilating surface blood vessels to expose more of the internal heat to the outside, and behavioral actions, such as removing clothes. In extreme situations, especially in hot arid environments, the body can lose enough water and salts in sweat to cause heat exhaustion, a condition consisting of muscle cramps, impairment of the cardiovascular system, unconsciousness, delirium, and death. Symptoms of heat exhaustion are increasing fatigue and weakness, excessive sweating, low blood pressure, cold, pale, and clammy skin, anxiety, and disorientation. A person with heat exhaustion can be helped by laying his or her body flat, or by tipping the head down to increase the blood supply to the brain while administering small amounts of sugar water to increase blood volume. Heat exhaustion can be prevented by adequate hydration before, during, and after physical activity.
Heat stroke (or sunstroke) can be induced by overexertion with prolonged exposure to a hot, humid environment, at environmental temperatures as low as 85 to 90 degrees Fahrenheit. In this case the body is unable to sweat due to the malfunctioning of the thermoregulatory control center in the brain. Tissue damage to the nervous and cardiovascular systems occurs when the core temperature rises above 109 degrees Fahrenheit, causing death. Symptoms of heat stroke may include headache, dizziness, fatigue, and awareness of the rapidly rising temperature. The person increases his or her rate of breathing to expel the excess heat and the heart races but the blood pressure is not affected. Sweating is typically decreased so the skin is hot, flushed, and usually dry. Treatment is aimed at cooling the person down and hospitalization is recommended to ensure that the thermoregulatory control center regains normal functioning. Heat exhaustion can quickly and unexpectedly lead to heat stroke and death even of the most physically fit, as was the case with offensive tackle Korey Stringer, who died in a Minnesota Vikings 2001 summer preseason practice. Although the body is well equipped to handle normal changes in body temperature, extreme changes in environmental conditions may not be able to be compensated for and can lead to irreversible damage and death.
See also: Causes of Death
Guyton, Arthur C., and John E. Hall. "Body Temperature, Temperature Regulation, and Fever." In Textbook of Medical Physiology, 10th edition. Philadelphia: W.B. Saunders, 2000.
Hardesty, Donald. The Archaeology of the Donner Party. Reno: University of Nevada Press, 1997.
DrugBase. "Heatstroke and Heat Exhaustion." In the DrugBase Guide to Medication [web site]. Available from www.drugbase.co.za/data/med_info/heatstr.htm.
NFL News. "Heatstroke Claims Life of Vikings All-Pro OT Stringer." In the NFL [web site]. Available from www.nfl.com/news/2001/MIN/stringer080101.html.
ALLISON K. WILSON