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Cardiorespiratory hysteresis during incremental high altitude ascent-descent quantifies the magnitude of ventilatory acclimatization
Leacy, Jack K.
Linares, Andrea M.
Zouboules, Shaelynn M.
Rampuri, Zahrah H.
Bird, Jordan D.
Herrington, Brittney A.
Mann, Leah M.
Soriano, Jan E.
Thrall, Scott F.
John Wiley & Sons, Inc. on behalf of the Physiological Society
Maintenance of arterial blood gases is achieved through sophisticated regulation of ventilation, mediated by central and peripheral chemoreflexes. Respiratory chemoreflexes are important during exposure to high altitude due to the competing influence of hypoxia and hypoxic hyperventilation‐mediated hypocapnia on steady‐state ventilatory drive. Inter‐individual variability exists in ventilatory acclimatization to high altitude, potentially affecting the development of acute mountain sickness (AMS). We aimed to quantify ventilatory acclimatization to high altitude by comparing differential ascent and descent values (i.e. hysteresis) in steady‐state cardiorespiratory variables. We hypothesized that (a) the hysteresis area formed by cardiorespiratory variables during ascent and descent would quantify the magnitude of ventilatory acclimatization, and (b) larger hysteresis areas would be associated with lower AMS symptom scores during ascent. In 25 healthy, Diamox‐free trekkers ascending to and descending from 5160 m, cardiorespiratory hysteresis was measured in the pressure of end‐tidal (PET)CO2, peripheral oxygen saturation (SpO2), minute ventilation (V̇E), chemoreceptor stimulus index (SI; PETCO2/SpO2) and the calculated steady‐state chemoreflex drive (SS‐CD; V̇E/SI) using portable devices (capnograph, peripheral pulse oximeter and respirometer, respectively). AMS symptoms were assessed daily using the Lake Louise Questionnaire. We found that (a) ascent‐descent hysteresis was present in all cardiorespiratory variables, (b) SS‐CD is a valid metric for tracking ventilatory acclimatization to high altitude and (c) highest AMS scores during ascent were significantly, moderately and inversely‐correlated to SS‐CD hysteresis magnitude (rs = ‐0.408, P = 0.043). We propose that ascent‐descent hysteresis is a novel and feasible way to quantify ventilatory acclimatization in trekkers during high altitude exposure.
Acute mountain sickness , High altitude , Hypoxia , Respiratory chemoreflexes , Ventilatory acclimatization
Leacy, J. K., Linares, A. M., Zouboules, S. M., Rampuri, Z. H., Bird, J. D., Herrington, B. A., Mann, L. M., Soriano, J. E., Thrall, S. F., Kalker, A. and Brutsaert, T. D. (2020) 'Cardiorespiratory hysteresis during incremental high altitude ascent‐descent quantifies the magnitude of ventilatory acclimatization', Experimental Physiology. doi: 10.1113/EP088488
© 2020, the Authors. Experimental Physiology © 2020 The Physiological Society. Published by John Wiley & Sons, Inc. This is the peer reviewed version of the following article: Leacy, J. K., Linares, A. M., Zouboules, S. M., Rampuri, Z. H., Bird, J. D., Herrington, B. A., Mann, L. M., Soriano, J. E., Thrall, S. F., Kalker, A. and Brutsaert, T. D. (2020) 'Cardiorespiratory hysteresis during incremental high altitude ascent‐descent quantifies the magnitude of ventilatory acclimatization', Experimental Physiology, doi: 10.1113/EP088488, which has been published in final form at https://doi.org/10.1113/EP088488. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.