Trans-cerebral HCO3 and PCO2 exchange during acute respiratory acidosis and exercise-induced metabolic acidosis in humans

Research output: Contribution to journalJournal articleResearchpeer-review

  • Caldwell, Hannah Grace
  • Ryan L Hoiland
  • Kurt J Smith
  • Patrice Brassard
  • Anthony R Bain
  • Michael M. Tymko
  • Connor A Howe
  • Jay M J R Carr
  • Benjamin S Stacey
  • Damian M Bailey
  • Audrey Drapeau
  • Mypinder S Sekhon
  • David B MacLeod
  • Philip N Ainslie

This study investigated trans-cerebral internal jugular venous-arterial bicarbonate ([HCO3]) and carbon dioxide tension (PCO2) exchange utilizing two separate interventions to induce acidosis: 1) acute respiratory acidosis via elevations in arterial PCO2 (PaCO2) (n = 39); and 2) metabolic acidosis via incremental cycling exercise to exhaustion (n = 24). During respiratory acidosis, arterial [HCO3] increased by 0.15 ± 0.05 mmol ⋅ l−1 per mmHg elevation in PaCO2 across a wide physiological range (35 to 60 mmHg PaCO2; P < 0.001). The narrowing of the venous-arterial [HCO3] and PCO2 differences with respiratory acidosis were both related to the hypercapnia-induced elevations in cerebral blood flow (CBF) (both P < 0.001; subset n = 27); thus, trans-cerebral [HCO3] exchange (CBF × venous-arterial [HCO3] difference) was reduced indicating a shift from net release toward net uptake of [HCO3] (P = 0.004). Arterial [HCO3] was reduced by −0.48 ± 0.15 mmol ⋅ l−1 per nmol ⋅ l−1 increase in arterial [H+] with exercise-induced acidosis (P < 0.001). There was no relationship between the venous-arterial [HCO3] difference and arterial [H+] with exercise-induced acidosis or CBF; therefore, trans-cerebral [HCO3] exchange was unaltered throughout exercise when indexed against arterial [H+] or pH (P = 0.933 and P = 0.896, respectively). These results indicate that increases and decreases in systemic [HCO3] – during acute respiratory/exercise-induced metabolic acidosis, respectively – differentially affect cerebrovascular acid-base balance (via trans-cerebral [HCO3] exchange).

Original languageEnglish
JournalJournal of Cerebral Blood Flow and Metabolism
Issue number4
Pages (from-to)559-571
Number of pages13
Publication statusPublished - 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© The Author(s) 2021.

    Research areas

  • Acidosis, Bicarbonate, Carbon dioxide, Exercise, Trans-cerebral exchange

ID: 306186439