(3) Evaporation. Evaporation is the conversion of any liquid to a gas. The
evaporation process requires energy (heat). Evaporation is the natural mechanism by
which sweating cools the body. This is why swimmers coming out of the water feel a
sensation of cold as the water evaporates from their skin. Individuals who exercise
vigorously in a cool environment may sweat and feel warm at first, but later, as their
sweat evaporates, they can become exceedingly cool.
(4) Radiation. Radiation is the loss of body heat directly to colder objects in
the environment. Because heat always travels from a warm object to a cooler one, a
person standing in a cold room will lose heat by radiation.
(5) Breathing. Breathing causes body heat to be lost as warm air in the
lungs is exhaled into the atmosphere and cooler air is inhaled.
If a person is working in an area that is hot due to the type of work being
done, such as in a steel mill, his body temperature will rise since the hot
environment is his "weather."
g. Time of Day Affects Body Temperature. A person's body temperature is
usually lower in the morning than in the afternoon. This change is mainly due to warmer
weather and more physical activity occurring later in the day.
h. Emotions Affect Body Temperature. A person that is excited (joyful,
scared, angry, and so forth.) will have an increase in body temperature. The excitement
causes the body to increase the rate at which it changes stored food (glucose and fat)
into usable energy. As the energy output increases, so does the amount of heat
produced by the body.
i. Place of Measurement Affects Measurement. The three locations normally
used in determining the body temperature are the mouth (oral temperature), the rectum
(rectal temperature), and the armpit (axillary temperature). If you measured a person's
body temperature using all three of these methods, you would obtain three slightly
different temperatures. The axillary (armpit) temperature would be slightly lower than
the oral (mouth) temperature while the rectal (rectum) temperature would be slightly
higher than the oral temperature. The rectal temperature is considered an essential
measurement in the hypothermic (cold injury) or hyperthermic (heat injury) patient. All
other methods of obtaining the body temperature are not considered accurate for the
pre-hospital or battlefield environment when dealing with environmental injuries. The
oral and axillary methods should be used for the clinical or field sick call settings only.