Time course and magnitude of ventilatory and renal acid-base acclimatization following rapid ascent to and residence at 3,800 m over nine days
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.; Skalk, Alexandra L.; Hewitt, Sarah A.; Steinback, Craig D.; Burns, David; Ondrus, Peter; Day, Trevor A.
Date:
2021-03-11
Copyright:
© 2021, Journal of Applied Physiology. All rights reserved.
Full text restriction information:
Access to this article is restricted until 12 months after publication by request of the publisher.
Restriction lift date:
2022-03-11
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
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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