Time course and magnitude of ventilatory and renal acid-base acclimatization following rapid ascent to and residence at 3,800 m over nine days

Jordan D. Bird, Jack K. Leacy, Glen E. Foster, Caroline A. Rickards, Richard J.A. Wilson, Ken D. O’Halloran, Nicholas G. Jendzjowsky, Brandon A. Pentz, Britta R.M. Byman, Scott F. Thrall, Alexandra L. Skalk, Sarah A. Hewitt, Craig D. Steinback, David Burns, Peter Ondrus, Trevor A. Day

Research output: Contribution to journalArticlepeer-review

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 (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.

Original languageEnglish
Pages (from-to)1705-1715
Number of pages11
JournalJournal of Applied Physiology
Volume130
Issue number6
DOIs
StatePublished - Jun 2021

Keywords

  • Acid-base
  • High altitude
  • Hypoxia
  • Renal compensation
  • Ventilatory acclimatization

Fingerprint

Dive into the research topics of 'Time course and magnitude of ventilatory and renal acid-base acclimatization following rapid ascent to and residence at 3,800 m over nine days'. Together they form a unique fingerprint.

Cite this