Thermodynamic state of the system "human body--closed medium" during a 240-day isolation in a hermetic chamber

Abstract

Temperature, humidity, and CO2 concentration in the atmosphere of a closed object were studied by the method of daily monitoring. The analysis of the results of monitoring was performed using a system with variation of body temperature (T) parameters of healthy subjects. Experimental data were obtained by the method of autothermotopometry in the state of rest (including rhythmic changes in these parameters during the morning–evening cycle) using medical thermometers. Four healthy volunteer subjects were tested. They were confined for 240 days to a simulator of the main unit of the Mir space station. Technogenic parameters of surrounding medium were ranked in accordance with a four-point scale of the degree of physiological impact (neutral–threshold–negative–significantly negative). The first stage of the two-factor analysis included the valuation of the state of the closed system medium (temperature–concentration of CO2). The second stage of the two-factor analysis included the evaluation of technogenic (i.e., attributed to surrounding medium) and physiological (i.e., attributed to human body) parameters of the system “human body–closed medium.” It was shown that, among eight parameters of thermal homeostasis (THS), a statistically significant correlation with technogenic parameters was observed for the parameter of deep body T (with CO2) and two T-gradients of human body (external longitudinal and internal radial) (with air T and CO2). According to the degree of strain of the body thermoregulation system in subjects, an increase in air T (above >23°) and a separate increase in the concentration of CO2 (above 0.4%) were found to be intermediate between threshold and negative physiological impacts. Combined application of the two factors distinctly potentiated a negative effect of surrounding medium on human body, the effect of carbon dioxide being more significant. Experimental evidence was obtained that factors of the closed environmental medium (falling within the normal range) exerted an unfavorable effect on the thermal balance of human body. This raises the problem of the revision of standards of basic physical parameters of surrounding medium in hermetic objects of various purposes.