ABSTRACT
The determination of body temperature is generally a noninvasive measurement; a thermometer can be inserted in the rectum, mouth, under the armpit, or in the ear canal. Normal oral body temperature is 98.6˚ F (37˚ C), although this value can vary over a 24-hour period due to the person’s metabolic state, the degree of exercise being engaged in, and the environmental temperature. Rectal temperature is about 1˚ higher than the orally measured value. Normal rectal temperatures can vary from 97˚ F due to prolonged cold exposure to 104˚ F as a result of strenuous exercise under hot environmental conditions. The body has several adaptive mechanisms (autonomic and behavioral) by which it maintains a relatively constant core temperature. To warm itself and conserve heat, the body may involuntarily shiver, voluntarily engage in aerobic exercise, and control heat loss by regulating blood flow to the extremities. To bring excess core temperature down, peripheral circulation can be increased to act as a radiator (this is effective only when the body temperature exceeds the air temperature), the body sweats, giving evaporative cooling, and the person ceases exercise and seeks shade. If the body cannot compensate for heat loss or gain, life is threatened. For example, prolonged immersion in cold water can result in profound hypothermia leading to death. However, the core temperature can drop to less than 75˚ F and the patient can still be revived. Prolonged temperatures over 105˚ F can produce heat stroke and brain lesions, and death is almost certain for temperatures over 110˚ F (Guyton, 1991).
