One of the main conditions for the normal course of all life processes in the human body is the principle of temperature constancy, in violation of which the development of severe, sometimes irreversible, changes is possible. A person is not defenseless against unfavorable temperature effects, since he has a perfect thermoregulation mechanism, which allows preserving isothermy with significant fluctuations in air temperature. The average limit of temperature fluctuations of our
Ganism, in which it remains viable, is relatively small and is in the range from + 25o to + 42o C.
As you know, the body’s heat transfer is associated with the generation of thermal energy and its transfer to the external environment by balancing the processes of chemical and physical thermoregulation . The first of them is determined by the intensity of metabolic processes, and the heat production does not change at air temperature in the range from + 15o to + 25o С, increases when it falls below + 15o С and decreases when it rises to + 25o– + 35o С. an increase in air temperature above + 35 ° C indicates a secondary increase in the basal metabolic rate, which already indicates a violation of chemical thermoregulation.
Simultaneously with the processes of heat accumulation in the body, it is continuously being transferred to the external environment (physical thermoregulation). Heat transfer is carried out in the following ways:
• heat radiation from the human body (in relation to surrounding surfaces having a lower temperature);
• carrying out – heat transfer by means of contact of a human body with the surrounding air (convection) or with objects and enclosing surfaces (conduction);
• evaporation of moisture from the surface of the skin and respiratory tract. At rest, at an air temperature of about + 20 ° C, heat radiation accounts for 50–65%, moisture evaporation 20–25%, convection 15% of the total heat loss by the body. Excessive heat loss in some cases causes a violation of tissue trophism (myositis, neuritis), in others – overcooling plays the role of a reflex factor that reduces the resistance of the whole organism, contributes to the development of pathological conditions of both infectious and non-infectious nature. At the same time, relatively short-term hypothermia with a gradual decrease in the patient’s body temperature to + 25 ° C is used in some surgical operations. Overheating of the body can lead to very serious consequences. In this case, mild and severe forms of hyperthermia are usually distinguished, the first of which is characterized by an increase in body temperature to + 38o– + 39o C, increased pulse and respiration, headache, general weakness, etc. In the second form, a significantly higher temperature rise (up to + 40o– + 41o C) is observed, which leads to direct damage to tissues, especially the central nervous system. Nausea and vomiting precede a shock stage with a deep loss of consciousness, sometimes accompanied by convulsions. Due to the violation of thermoregulation of central genesis, the formation of sweat is reduced. This severe form of overheating of the body, called heat stroke, can result in a sudden onset of a coma and the death of the victim.
Less abrupt, but lasting changes in external temperature conditions (for example, in production) can have an adverse effect on the body due to overvoltage of the thermoregulatory apparatus and violation of the heat balance. The latter, for example, relates to workers in hot shops, miners and miners who are in deep mines under conditions of elevated air temperature; working conditions of loggers, divers, fishermen, builders in certain seasons of the year are associated with the danger of hypothermia.
It should be noted the value of not only the absolute value of air temperature, but also the amplitude of its oscillations. The more often these vibrations are repeated, and the sharper they are, the more difficult the body adapts to them and the more efforts are spent on maintaining isothermy. Therefore, the doctor should be interested in the dynamics of temperature fluctuations, which is often hidden behind the average data of meteorological reports.