Key result
Acute simulated hypobaric hypoxia linked to a ~31% reduction in RMSSD versus normoxia.
Why the study?
Investigating autonomic nervous system responses to acute hypoxic exposure may provide insight into the cardiopulmonary system adjustment mechanisms during acclimatization.
Does acute exposure to a hypobaric hypoxic environment alter heart rate variability and autonomic nervous system regulation in healthy young subjects?
Observational (n=33)
No
Does acute exposure to a hypobaric hypoxic environment alter heart rate variability and autonomic nervous system regulation in healthy young subjects?
Acute exposure to hypobaric hypoxia in healthy young adults leads to sympathetic activation, elevated heart rate, and reduced overall HRV complexity, which recovers upon return to normoxia.
Answers are grounded in this paper and cite their sources.
Acute hypobaric hypoxia was associated with reduced HRV in healthy young adults; hypothesis-generating for autonomic effects and requires confirmation before clinical consideration.
Background: The autonomic nervous system (ANS) is crucial for acclimatization. Investigating the responses of acute exposure to a hypoxic environment may provide some knowledge of the cardiopulmonary system’s adjustment mechanism. Objective : The present study investigates the longitudinal changes and recovery in heart rate variability (HRV) in a young healthy population when exposed to a simulated plateau environment. Methods : The study followed a strict experimental paradigm in which physiological signals were collected from 33 healthy college students (26 ± 2 years, 171 cm ± 7 cm, 64 ± 11 kg) using a medical-grade wearable device. The subjects were asked to sit in normoxic (approximately 101 kPa) and hypoxic (4,000 m above sea level, about 62 kPa) environments. The whole experimental process was divided into four stable resting measurement segments in chronological order to analyze the longitudinal changes of physical stress and recovery phases. Seventy-six time-domain, frequency-domain, and non-linear indicators characterizing rhythm variability were analyzed in the four groups. Results: Compared to normobaric normoxia, participants in hypobaric hypoxia had significantly lower HRV time-domain metrics, such as RMSSD, MeanNN, and MedianNN ( p < 0.01), substantially higher frequency domain metrics such as LF/HF ratio ( p < 0.05), significantly lower Poincaré plot parameters such as SD1/SD2 ratio and other Poincaré plot parameters are reduced considerably ( p < 0.01), and Refined Composite Multi-Scale Entropy (RCMSE) curves are reduced significantly ( p < 0.01). Conclusion: The present study shows that elevated heart rates, sympathetic activation, and reduced overall complexity were observed in healthy subjects exposed to a hypobaric and hypoxic environment. Moreover, the results indicated that Multiscale Entropy (MSE) analysis of RR interval series could characterize the degree of minor physiological changes. This novel index of HRV can better explain changes in the human ANS.
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Ma et al. (2022) conducted an observational in Healthy (n=33). Hypobaric hypoxic environment (4,000 m above sea level) vs. Normobaric normoxia (sea level) was evaluated on Root mean square of successive RR interval differences (RMSSD) (p=<0.001). Acute exposure to a simulated hypobaric hypoxic environment significantly reduced heart rate variability time-domain metrics, including a decrease in RMSSD compared to normobaric normoxia.
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