Effects of simulated high altitude on body temperature and heart rate in pilot reserves during the hot-dry exposure

Recent research has primarily focused on human thermoregulatory responses at high altitudes, but investigations involving extremely high-temperature and hypobaric compound environments are currently lacking. To address this gap in knowledge, this study aimed to enhance the prediction of human heat sensation for pilot reserves while operating in extremely hot cabins with decompression. To achieve this, an improved Predicted Heat Strain (PHS) model was developed by incorporating the influence of air pressure on metabolic rate. The model's validity was assessed through experiments conducted at different altitudes (0m, 5000m, and 8000m) and varying environmental conditions (26°C and 45 °C, 10% RH and 40% RH) within an environmental simulation cabin. During these experiments, local skin temperature, core temperature, heart rate, and blood oxygen saturation were measured. The findings revealed distinct variations in the skin temperature of the hand and foot segments across different experimental stages, and significant correlations were observed between heart rate, core temperature, and local skin temperatures. Furthermore, regression models were established to explore the relationship between heart rate and local skin temperatures. By comparing simulated and experimental core and local skin temperatures, the enhanced PHS model was successfully validated. The conclusions drawn from this study provide valuable insights for predicting thermal physiological indices accurately and conveniently in hot-dry and hypobaric environments.