The Effects of Altitude-related Hypoxia Exposure on the Multiscale Dynamics of Blood Pressure Fluctuation During Sleep: The Observation from a Pilot Study

Qian Li; Zhenxiang Guo; Fuzheng Liu; Ye Liu; Dapeng Bao; Junhong Zhou

doi:10.2147/NSS.S319031

The Effects of Altitude-related Hypoxia Exposure on the Multiscale Dynamics of Blood Pressure Fluctuation During Sleep: The Observation from a Pilot Study

Nat Sci Sleep. 2021 Jul 15:13:1147-1155. doi: 10.2147/NSS.S319031. eCollection 2021.

Authors

Qian Li^#¹, Zhenxiang Guo^#¹, Fuzheng Liu², Ye Liu³, Dapeng Bao⁴, Junhong Zhou⁵

Affiliations

¹ Sports Coaching College, Beijing Sport University, Beijing, People's Republic of China.
² School of Medical Humanities, Capital Medical University, Beijing, People's Republic of China.
³ National Team Performance Training Center, National Sports Training Center, General Administration of Sport of China, Beijing, People's Republic of China.
⁴ China Institute of Sport and Health Science, Beijing Sport University, Beijing, People's Republic of China.
⁵ Hebrew SeniorLife Hinda and Arthur Marcus Institute for Aging Research, Harvard Medical School, Boston, MA, 02131, USA.

^# Contributed equally.

Abstract

Purpose: The purpose exposure to hypoxia in high altitudes severely impairs the sleep quality and the related cardiovascular regulation, including the blood pressure (BP) regulation. BP regulation depends upon the continuous interaction of components over multiple temporal scales. As such, the dynamics of BP fluctuation are complex, and BP complexity has been linked to several pathological events. However, the effects of the exposure to hypoxia on BP complexity during sleep remain unknown.

Methods: Twenty-five younger men naïve to high-altitude sleep (apnea severity as assessed by hypoxia apnea index (AHI): normal=8; moderate=9; severe=8) completed one nocturnal sleep under each of the three altitudes: 0 (ie, baseline), 2000, and 4000 m. The sleep characteristics and oxygen saturation (ie, SpO₂) were assessed using polysomnography (PSG). The beat-to-beat BP fluctuation was recorded using a finger-blood-pressure sensor. Multiscale entropy (MSE) was used to characterize the complexity of systolic (SBP) and diastolic (DBP) BP fluctuations, and lower MSE reflected lower complexity.

Results: Compared to 0-m condition, SBP (p=0.0003) and DBP (F=12.1, p=0.0002) complexity, SpO₂ (p<0.0001) and REM ratio (p<0.0090) were decreased, AHI was increased (p=0.0004) in 2000-m and even more in 4000-m conditions. In addition, lower BP complexity was associated with greater AHI (r=-0.66~0.52, p=0.0010), lower SpO₂ (r=0.48~0.51, p=0.0100~0.0200) and lower REM ratio (r=0.48~0.52, p=0.0200). Participants with greater percent reduction in BP complexity between altitudes had greater percent reduction in REM ratio and SpO₂ (r=0.38~0.45, p=0.0090~0.0200), after adjustment for age, BMI, baseline apnea and altitude.

Conclusion: These results suggested that the characterization of BP complexity may provide novel insights into the underlying mechanisms through which the exposure to hypoxia affects cardiovascular health during sleep, as well as sleep quality. This BP complexity may serve as a novel marker to help the management of cardiovascular health and sleep quality in high-altitude living.

Keywords: beat-to-beat blood pressure; high altitude; multiscale entropy; sleep quality.

Grants and funding

This study was supported by Specialized Research Fund for the Doctoral Program of Higher Education of China (20131112120007).