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Time course and magnitude of ventilatory and renal acid-base acclimatization following rapid ascent to and residence at 3,800 m over nine days
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Accepted Version
Date
2021-03-11
Authors
Bird, Jordan D.
Leacy, Jack K.
Foster, Glen Edward
Rickards, Caroline A.
Wilson, Richard J. A.
O'Halloran, Ken D.
Jendzjowsky, Nicholas G.
Pentz, Brandon A.
Byman, Britta R. M.
Thrall, Scott F.
Journal Title
Journal ISSN
Volume Title
Publisher
American Physiological Society
Published Version
Abstract
Rapid ascent to high altitude imposes an acute hypoxic and acid-base challenge, with ventilatory and renal acclimatization countering these perturbations. Specifically, ventilatory acclimatization improves oxygenation, but with concomitant hypocapnia and respiratory alkalosis. A compensatory, renally-mediated relative metabolic acidosis follows via bicarbonate elimination, normalizing arterial pH(a). The time-course and magnitude of these integrated acclimatization processes are highly variable between individuals. Using a previously-developed metric of renal reactivity (RR), indexing the change in arterial bicarbonate concentration (∆[HCO3-]a; renal response) over the change in arterial pressure of CO2 (∆PaCO2; renal stimulus), we aimed to characterize changes in RR magnitude following rapid ascent and residence at altitude. Resident lowlanders (n=16) were tested at 1,045 m (Day [D]0) prior to ascent, on D2 within 24-hours of arrival, and D9 during residence at 3,800 m. Radial artery blood draws were obtained to measure acid-base variables: PaCO2, [HCO3-]a and pHa. Compared to D0, PaCO2 and [HCO3-]a were lower on D2 (P<0.01) and D9 (P<0.01), whereas significant changes in pHa (P>0.058) and RR (P=0.056) were not detected. As pHa appeared fully compensated on D2 and RR did not increase significantly from D2 to D9, these data demonstrate renal acid-base compensation within 24-hours at moderate steady-state altitude. Moreover, RR was strongly and inversely correlated with ∆pHa on D2 and D9 (r≤-0.95; P<0.0001), suggesting that a high-gain renal response better protects pHa. Our study highlights the differential time-course, magnitude, and variability of integrated ventilatory and renal acid-base acclimatization following rapid ascent and residence at high altitude.
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Keywords
High altitude , Hypoxia , Ventilatory acclimatization , Acid-base , Renal compensation
Citation
Bird, J. D., Leacy, J. K., Foster, G. E., Rickards, C. A., Wilson, R. J. A., O'Halloran, K. D., Jendzjowsky, N. G., Pentz, B. A., Byman, B. R. M., Thrall, S. F., Skalk, A. L., Hewitt, S. A., Steinback, C. D., Burns, D., Ondrus, P. and Day, T. A. (2021) 'Time course and magnitude of ventilatory and renal acid-base acclimatization following rapid ascent to and residence at 3,800 m over nine days', Journal of Applied Physiology. doi: 10.1152/japplphysiol.00973.2020
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© 2021, Journal of Applied Physiology. All rights reserved.