Barometric pressure change and heart rate response during sleeping at ~ 3000 m altitude
We investigated effects of change in barometric pressure (P B) with climate change on heart rate (HR) during sleep at 3000 m altitude. Nineteen healthy adults (15 males and four females; mean age 32 years) participated in this study. We measured P B (barometry) and HR (electrocardiography) every minute during their overnight stay in a mountain lodge at ~ 3000 m. We also measured resting arterial oxygen saturation (SpO2) and evaluated symptoms of acute mountain sickness (AMS) by using the Lake Louise Questionnaire at 2305 and 3000 m, respectively. P B gradually decreased during the night at the speed of approximately − 0.5 hPa/h. We found that HR during sleep decreased linearly as P B decreased in all subjects, with significance (r = 0.492–0.893; all, P < 0.001). Moreover, cross correlation analysis revealed that HR started to decrease after ~ 15 min following the decrease in P B, on average. SpO2 was 93.8 ± 1.7% at 2305 m before climbing, then decreased significantly to 90.2 ± 2.2% at the lodge before going to bed, and further decreased to 87.5 ± 2.7% after waking (all, P < 0.05). Four of the 19 subjects showed a symptom of AMS after waking (21%). Further, the decrease in HR in response to a given decrease in P B (ΔHR/ΔPB) was negatively related with a decrease in SpO2 from before going to bed to after waking at 3000 m (r = − 0.579, P = 0.009) and with total AMS scores after waking (r = 0.489, P = 0.033).
KeywordsAcute mountain sickness Arterial O2 saturation Time delay Cardiovascular responses Hypoxemia
We thank all participants for their time and effort. We also thank Dr. Tadashi Uno, Dr. Tatsuya Hasegawa, Miss Sakura Nakano, and Mrs. Mayuka Furihata for their technical assistance.
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