TY - JOUR
T1 - Time course and magnitude of ventilatory and renal acid-base acclimatization following rapid ascent to and residence at 3,800 m over nine days
AU - Bird, Jordan D.
AU - Leacy, Jack K.
AU - Foster, Glen E.
AU - Rickards, Caroline A.
AU - Wilson, Richard J.A.
AU - O’Halloran, Ken D.
AU - Jendzjowsky, Nicholas G.
AU - Pentz, Brandon A.
AU - Byman, Britta R.M.
AU - Thrall, Scott F.
AU - Skalk, Alexandra L.
AU - Hewitt, Sarah A.
AU - Steinback, Craig D.
AU - Burns, David
AU - Ondrus, Peter
AU - Day, Trevor A.
N1 - Funding Information:
Financial support for this study was provided by the Alberta Government Student Temporary Employment Program, Natural Sciences and Engineering Research Council of Canada (NSERC) Undergraduate Student Research Assistantships. In addition, funding was also provided by the Natural Sciences and Engineering Research Council of Canada Discovery grants (C. D. Steinback: RGPIN 06637; T. A. Day: RGPIN 04915; R. J. A. Wilson: RGPIN-03941). G. E. Foster is a Michael Smith Foundation for Health Research Scholar. J. K. Leacy was funded by the Department of Physiology, University College Cork. C. D. Steinback is funded by a Heart and Stroke Foundation of Canada Joint National and Alberta New Investigator Award (Steinback). N. G. Jendzjowsky was funded by an NSERC BRAIN CREATE Program and a Parker B. Francis Foundation Postdoctoral Fellowship. C. A. Rickards was funded by an American Heart Association Grant-in-Aid (17GRNT33671110). Additional funding for the expedition was obtained from a University of Calgary University Research Grants Committee (URGC) grant.
Publisher Copyright:
Copyright © 2021 the American Physiological Society
PY - 2021/6
Y1 - 2021/6
N2 - 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 (D[HCO3-]a; renal response) over the change in arterial pressure of CO2 (DPaCO2; 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 h 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 with D0, PaCO2 and [HCO3-]a were lower on D2 (P < 0.01) and D9 (P < 0.01), whereas significant changes in pHa (P = 0.072) 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 h at moderate steady-state altitude. Moreover, RR was strongly and inversely correlated with DpHa 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. NEW & NOTEWORTHY We assessed the time course, magnitude, and variability of integrated ventilatory and renal acid-base acclimatization with rapid ascent and residence at 3,800 m. Despite reductions in PaCO2 upon ascent, pHa was normalized within 24 h of arrival at 3,800 m through renal compensation (i.e., bicarbonate elimination). Renal reactivity (RR) was unchanged between days 2 and 9, suggesting a lack of plasticity at moderate steady-state altitude. RR was strongly correlated with DpHa, suggesting that a high-gain renal response better protects pHa.
AB - 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 (D[HCO3-]a; renal response) over the change in arterial pressure of CO2 (DPaCO2; 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 h 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 with D0, PaCO2 and [HCO3-]a were lower on D2 (P < 0.01) and D9 (P < 0.01), whereas significant changes in pHa (P = 0.072) 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 h at moderate steady-state altitude. Moreover, RR was strongly and inversely correlated with DpHa 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. NEW & NOTEWORTHY We assessed the time course, magnitude, and variability of integrated ventilatory and renal acid-base acclimatization with rapid ascent and residence at 3,800 m. Despite reductions in PaCO2 upon ascent, pHa was normalized within 24 h of arrival at 3,800 m through renal compensation (i.e., bicarbonate elimination). Renal reactivity (RR) was unchanged between days 2 and 9, suggesting a lack of plasticity at moderate steady-state altitude. RR was strongly correlated with DpHa, suggesting that a high-gain renal response better protects pHa.
KW - Acid-base
KW - High altitude
KW - Hypoxia
KW - Renal compensation
KW - Ventilatory acclimatization
UR - http://www.scopus.com/inward/record.url?scp=85108387154&partnerID=8YFLogxK
U2 - 10.1152/japplphysiol.00973.2020
DO - 10.1152/japplphysiol.00973.2020
M3 - Article
C2 - 33703943
AN - SCOPUS:85108387154
SN - 8750-7587
VL - 130
SP - 1705
EP - 1715
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 6
ER -