Physiological response to typical temperature step-changes in winter of China

This study mainly explored human health and thermal comfort associated physiological response to temperature step-changes in winter. Several physiological parameters, including blood pressure, blood oxygen saturation (SPO2), skin temperature and electrocardiograph (ECG), were measured to exam human reactions to temperature alterations of different intensities and directions. Three temperature step-change conditions (S10: 20 °C; 10 °C; 20 °C, S20: 20 °C; 0 °C; 20 °C, S40: 20 °C; −20 °C; 20 °C) were developed with 18 healthy subjects recruited. Statistical analysis shows that blood pressure is sensitive to temperature steps since significance is detected for values before and after step-changes in all three conditions. The increase in systolic pressure after sudden cooling in the large down-step (S40) reached 18 mm Hg, around fourfold and twice that in small (S10) and medium steps (S20), respectively. Besides, systolic pressure appears to be more responsive than diastolic pressure. Instant change in skin temperature caused by down-step is remarkably larger than that by up-steps. More than 45 min were demanded for skin temperature to become stable after 15 min' exposure in −20 °C. In S20 and S40, the ration of LF (low frequency power) to HF (high frequency power) of ECG underwent remarkable decrease after sudden cooling, and vice versa.