Acid‐Base Compensation During Incremental Ascent to High Altitude
Bibliographic record
Abstract
Ascent to high altitude, and the associated hypoxic ventilatory response, imposes an acid‐base challenge, namely chronic hypocapnia and respiratory alkalosis. The kidneys act to compensate for this respiratory alkalosis via bicarbonate (HCO 3 − ) excretion in urine to induce a compensatory metabolic acidosis. Although the importance of renal responsiveness through acid‐base modifications is well‐defined, the time course and extent of plasticity in this response during incremental ascent to altitude is unclear. Thus, we developed a practical index of renal reactivity (RR), indexing the relative change in arterial HCO 3 − concentration ([HCO 3 − ] a ; i.e., response) against the relative change in arterial partial pressure of CO 2 (PaCO 2 ; i.e., stimulus) during incremental ascent to high altitude (RR=Δ[HCO 3 − ] a /ΔPaCO 2 ). We sought to assess (1) if RR increased over time and with incremental ascent to high altitude and (2) if RR was correlated with relative changes in arterial pH (ΔpH a ) throughout ascent. During ascent to 5160 m over 10 days in the Nepal Himalaya, arterial blood was drawn from the radial artery for measurement of acid‐base variables (Abbott i‐STAT portable blood gas/electrolyte analyzer; CG4+ and CHEM8+ cartridges) in lowlanders at 1045/1400 m (baseline) and at four different altitudes following one‐night sleep: 3440 m (n=18), 3820 m (n=17), 4370 m (n=15) and 5160 m (n=13). At 3820 m (day five of altitude exposure) and higher, RR significantly increased and plateaued in comparison to 3440 m (day three of altitude exposure; P<0.04), suggesting plasticity in renal acid‐base compensation. At all four altitudes, we observed a strong correlation (range: r=−0.71 to −0.98; P<0.001) between RR and relative ΔpH a from baseline, suggesting that the RR index accurately quantified acid‐base responsiveness via renal mechanisms throughout ascent. In conclusion, renal acid‐base compensation mechanisms demonstrate plasticity and a unique time course during incremental ascent to high altitude, which was detected using a novel RR index. The extent of plasticity and plateau in renal responsiveness may predict severity of altitude illness or acclimatization at higher or more prolonged stays at altitude. Support or Funding Information This work was supported by (a) Alberta Government Student Temporary Employment Program, (b) Alberta Innovates Health Solutions Summer Studentship, and (c) Natural Sciences and Engineering Research Council of Canada Discovery grant. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".