Effects of acute hypobaric hypoxia on thermoregulatory and circulatory responses during cold air exposure
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(2020) 39:28
SHORT REPORT
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Effects of acute hypobaric hypoxia on thermoregulatory and circulatory responses during cold air exposure Sora Shin1, Yoshiki Yasukochi2, Hitoshi Wakabayashi3 and Takafumi Maeda4,5*
Abstract Background: The thermoregulatory responses during simultaneous exposure to hypoxia and cold are not well understood owing to the opposite reactions of vasomotor tone in these two environments. Therefore, the purpose of this study was to investigate the influences of hypobaric hypoxia on various thermoregulatory responses, including skin blood flow (SkBF) during cold exposure. Methods: Ten subjects participated in two experimental conditions: normobaric normoxia with cold (NC, barometric pressure (PB) = 760 mmHg) and hypobaric hypoxia with cold (HC, PB = 493 mmHg). The air temperature was maintained at 28 °C for 65 min and gradually decreased to 19 °C for both conditions. The total duration of the experiment was 135 min. Results: The saturation of percutaneous oxygen (SpO2) was maintained at 98–99% in NC condition, but decreased to around 84% in HC condition. The rectal and mean skin temperatures showed no significant differences between the conditions; however, the forehead temperature was higher in HC condition than in NC condition. The pulse rate increased in HC condition, and there was a strong negative relationship between SpO2 and pulse rate (r = − 0.860, p = 0.013). SkBF and blood pressure showed no significant differences between the two conditions. Conclusion: These results suggest that hypobaric hypoxia during cold exposure did not alter the overall thermoregulatory responses. However, hypobaric hypoxia did affect pulse rate regardless of cold exposure. Keywords: Cold stress, Altitude, Thermoregulation, Skin temperature, Individual differences
Background When the human body is exposed to cold, skin blood flow (SkBF) decreases to minimize the heat loss from the body to the environment [1]. This thermoregulatory adjustment changes skin temperature (Tsk), causing it to decline. Further, if the heat storage cannot be maintained, rectal temperature (Tre) decreases. However, the thermoregulatory responses during simultaneous exposure to * Correspondence: [email protected] 4 Department of Human Science, Faculty of Design, Kyushu University, 4-9-1 Shiobaru, Minami-ku, Fukuoka 815-8540, Japan 5 Physiological Anthropology Research Center, Faculty of Design, Kyushu University, 4-9-1 Shiobaru, Minami-ku, Fukuoka 815-8540, Japan Full list of author information is available at the end of the article
hypobaric hypoxia and cold are rather equivocal. This stems from the fact that local tissue hypoxia elicits an increase in blood flow in order to maintain the usual oxygen delivery rate for sustained metabolism [2]. Previous studies have shown the changes in Tre and mean Tsk during simultaneous exposure to hypoxia and cold. Fukazawa et al. [3] reported no significant differences on Tre, but higher mean Tsk at 17 °C and a simulated altitude of 5000 m compared to normobaric normoxia. Bl
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