期刊
JOURNAL OF APPLIED PHYSIOLOGY
卷 130, 期 6, 页码 1705-1715出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00973.2020
关键词
acid-base; high altitude; hypoxia; renal compensation; ventilatory acclimatization
资金
- Alberta Government Student Temporary Employment Program
- Natural Sciences and Engineering Research Council of Canada (NSERC) Undergraduate Student Research Assistantships
- Natural Sciences and Engineering Research Council of Canada [RGPIN 06637, RGPIN 04915, RGPIN-03941]
- Michael Smith Foundation for Health Research Scholar - Department of Physiology, University College Cork
- Heart and Stroke Foundation of Canada Joint National and Alberta New Investigator Award - NSERC BRAIN CREATE Program
- Parker B. Francis Foundation - American Heart Association [17GRNT33671110]
- University of Calgary University Research Grants Committee (URGC) grant
Rapid ascent to high altitude poses challenges of acute hypoxia and acid-base disturbances, which are countered by ventilatory and renal acclimatization. Renal compensation through bicarbonate elimination helps in normalizing arterial pH. The time course and magnitude of these adaptation processes can vary widely between individuals.
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 (Delta[HCO3-]a; renal response) over the change in arterial pressure of CO2 (Delta Pa-CO(2); 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: Pa-CO(2), [HCO3-]a, and pHa. Compared with DO, Pa-CO(2) 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 Delta 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. 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 Pa-CO(2) 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 Delta pHa, suggesting that a high-gain renal response better protects pHa.
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