Effects of hypobaric hypoxia on human physiological and psychological responses in hot-humid environments

Abstract

The hot-humid and hypobaric hypoxic environment hampers human physiological and psychological responses. In this study, 10 healthy participants were recruited to walk on a treadmill at 4 km/h in a hypobaric chamber under nine experimental conditions involving three air temperatures (Ta = 33, 37, and 40 °C), and three barometric pressures (PB = 96.5, 65.7, and 63.2 kPa). At 33 and 37 °C, the mean skin temperature, oral temperature, and sweat rate were not significantly affected by hypobaric hypoxia. The diastolic blood pressure, systolic blood pressure, and oxygen saturation decreased significantly, while the heart rate increased significantly under hypobaric hypoxic conditions. At 40 °C, the heart rate and diastolic blood pressure were not significantly affected by hypobaric hypoxia, while the oral temperature was significantly higher at 63.2 kPa than at 65.7 and 95.6 kPa. The remaining physiological parameters exhibited similar patterns as those at 33 and 37 °C. In conclusion, higher Ta had the most substantial effects on the cardiovascular system. Additionally, individuals should not work in environments where the Ta exceeds the body core temperature, especially at higher altitudes, as the risk of heat-related injuries could increase. At various Ta, the thermal sensation and acceptability were not significantly affected by hypobaric hypoxia, while a decrease in PB to 63.2 kPa resulted in a significant increase in tolerance, along with a notable reduction in exposure time. Therefore, this study provides valuable information concerning the physiological and psychological responses of humans exposed to working conditions similar to those tested.