Horiuchi M, Dobashi S, Kiuchi M, Fukuoka Y, Koyama K. Hypoxic-induced resting ventilatory and circulatory responses under multistep hypoxia is related to decline in peak aerobic capacity in hypoxia.
J Physiol Anthropol 2022;
41:36. [PMID:
36280884 PMCID:
PMC9590180 DOI:
10.1186/s40101-022-00310-3]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Accepted: 10/07/2022] [Indexed: 11/07/2022] Open
Abstract
Background
Several factors have been shown to contribute to hypoxic-induced declined in aerobic capacity. In the present study, we investigated the effects of resting hypoxic ventilatory and cardiac responses (HVR and HCR) on hypoxic-induced declines in peak oxygen uptake (\documentclass[12pt]{minimal}
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\begin{document}$$\dot{\mathrm V}$$\end{document}V˙O2peak).
Methods
Peak oxygen uptakes was measured in normobaric normoxia (room air) and hypoxia (14.1% O2) for 10 young healthy men. The resting HVR and HCR were evaluated at multiple steps of hypoxia (1 h at each of 21, 18, 15 and 12% O2). Arterial desaturation (ΔSaO2) was calculate by the difference between SaO2 at normoxia—at each level of hypoxia (%). HVR was calculate by differences in pulmonary ventilation between normoxia and each level of hypoxia against ΔSaO2 (L min−1 %−1 kg−1). Similarly, HCR was calculated by differences in heart rate between normoxia and each level of hypoxia against ΔSaO2 (beats min−1 %−1).
Results
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\begin{document}$$\dot{\mathrm V}$$\end{document}V˙O2peak significantly decreased in hypoxia by 21% on average (P < 0.001). HVR was not associated with changes in \documentclass[12pt]{minimal}
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\begin{document}$$\dot{\mathrm V}$$\end{document}V˙O2peak. ΔSaO2 from normoxia to 18% or 15% O2 and HCR between normoxia and 12% O2 were associated with changes in \documentclass[12pt]{minimal}
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\begin{document}$$\dot{\mathrm V}$$\end{document}V˙O2peak (P < 0.05, respectively). The most optimal model using multiple linear regression analysis found that ΔHCR at 12% O2 and ΔSaO2 at 15% O2 were explanatory variables (adjusted R2 = 0.580, P = 0.02).
Conclusion
These results suggest that arterial desaturation at moderate hypoxia and heart rate responses at severe hypoxia may account for hypoxic-induced declines in peak aerobic capacity, but ventilatory responses may be unrelated.
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