Complex of computer models for cold stress evaluation in water

Abstract

Introduction. Due to the high value of water thermal conductivity comparing to air, stay of man in cold water (water temperature lower than 25 sup>°C) is associated with high life and health hazard. One of the ways to evaluate survival time of human in water is usage of statistics data about survivors and water temperature organized as tables and curves. Another method to evaluate survival time and physiological state of man in water is computer modelling of human thermoregulatory system. Computer modelling allows to predict human thermal state in extreme environment without health hazard for man. Main body. Information technology based on complex of mathematical models was developed to predict human thermophysiological state in cold water. The main component of complex is mathematical model of shivering in muscles. Shivering increases heat production up to four-fivefold of basal metabolic rate. Human thermophysiological state in case of accidental water immersion at temperature range from 5 to 25 °C was predicted using information technology. In order to evaluate influence of immersion level on hypothermia, computer modelling was performed for cases of full immersion, head out of water and immersion with head and arms out of water. Conclusions. Developed complex of computer models allows to predict human thermophysiological state and evaluate cold stress in wide range of water temperature and the immersion level. The modelling results showed that the cooling rate increases with reduction in water temperature and the increase in percentage of immersed human body. When water temperature below 25 °C heat loss is always higher than shivering in muscles, thus body core temperature reduces at all levels of immersion. The safest case of immersion is immersion with head and arms out of water.