Low frequency ventilatory oscillations in hypoxia are a major contributor of the low frequency component of heart rate variability Running head: Cardiorespiratory coupling at exercise in hypoxia
Résumé
Heart rate variability (HRV) may be influenced by several factors, such as environment (hypoxia, hyperoxia, hypercapnia) or physiological demand (exercise). In this retrospective study, we tested the hypothesis that inter-beats (RR) intervals in healthy subjects exercising under various environmental stresses exhibit oscillations at the same frequency than ventilatory oscillations. Methods Spectra from RR intervals and ventilation (E) were collected from 37 healthy young male subjects who participated in five previous studies focused on ventilatory oscillations (or periodic breathing) during exercise in hypoxia, hyperoxia and hypercapnia. Bland & Altman test and multivariate regressions were then performed to compare respective frequencies and changes in peak powers of the two signals. Results Fast Fourier analysis of RR and E signals showed that RR was oscillating at the same frequency than periodic breathing, i.e. ~0.09 Hz (11 seconds). During exercise, in these various conditions, the difference between minimum and maximum HRV peak power was positively correlated to the same change in ventilation peak power (P < 0.05). Low Frequency (LF) peak power was correlated to tidal volume (P < 0.01) and breathing frequency (P < 0.001). Conclusions This study suggests that low frequency ventilatory oscillations in hypoxia are a major contributor of the LF band power of heart rate variability.
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