Trans-cerebral HCO <sub>3</sub> <sup>−</sup> and PCO <sub>2</sub> exchange during acute respiratory acidosis and exercise-induced metabolic acidosis in humans
Bibliographic record
Abstract
This study investigated trans-cerebral internal jugular venous-arterial bicarbonate ([HCO 3 − ]) and carbon dioxide tension (PCO 2 ) exchange utilizing two separate interventions to induce acidosis: 1) acute respiratory acidosis via elevations in arterial PCO 2 (PaCO 2 ) (n = 39); and 2) metabolic acidosis via incremental cycling exercise to exhaustion (n = 24). During respiratory acidosis, arterial [HCO 3 − ] increased by 0.15 ± 0.05 mmol ⋅ l −1 per mmHg elevation in PaCO 2 across a wide physiological range (35 to 60 mmHg PaCO 2 ; P < 0.001). The narrowing of the venous-arterial [HCO 3 − ] and PCO 2 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 [HCO 3 − ] exchange (CBF × venous-arterial [HCO 3 − ] difference) was reduced indicating a shift from net release toward net uptake of [HCO 3 − ] (P = 0.004). Arterial [HCO 3 − ] 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 [HCO 3 − ] difference and arterial [H + ] with exercise-induced acidosis or CBF; therefore, trans-cerebral [HCO 3 − ] 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 [HCO 3 − ] – during acute respiratory/exercise-induced metabolic acidosis, respectively – differentially affect cerebrovascular acid-base balance (via trans-cerebral [HCO 3 − ] exchange).
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".