Evidence for direct <scp>CO<sub>2</sub></scp>‐mediated alterations in cerebral oxidative metabolism in humans
Bibliographic record
Abstract
Abstract Aim How the cerebral metabolic rates of oxygen and glucose utilization (CMRO 2 and CMR Glc , respectively) are affected by alterations in arterial PCO 2 (PaCO 2 ) is equivocal and therefore was the primary question of this study. Methods This retrospective analysis involved pooled data from four separate studies, involving 41 healthy adults (35 males/6 females). Participants completed stepwise steady‐state alterations in PaCO 2 ranging between 30 and 60 mmHg. The CMRO 2 and CMR Glc were assessed via the Fick approach (CBF × arterial‐internal jugular venous difference of oxygen or glucose content, respectively) utilizing duplex ultrasound of the internal carotid artery and vertebral artery to calculate cerebral blood flow (CBF). Results The CMRO 2 was altered by 0.5 mL × min −1 (95% CI: −0.6 to −0.3) per mmHg change in PaCO 2 ( p < 0.001) which corresponded to a 9.8% (95% CI: −13.2 to −6.5) change in CMRO 2 with a 9 mmHg change in PaCO 2 (inclusive of hypo‐ and hypercapnia). The CMR Glc was reduced by 7.7% (95% CI: −15.4 to −0.08, p = 0.045; i.e., reduction in net glucose uptake) and the oxidative glucose index (ratio of oxygen to glucose uptake) was reduced by 5.6% (95% CI: −11.2 to 0.06, p = 0.049) with a + 9 mmHg increase in PaCO 2 . Conclusion Collectively, the CMRO 2 is altered by approximately 1% per mmHg change in PaCO 2 . Further, glucose is incompletely oxidized during hypercapnia, indicating reductions in CMRO 2 are either met by compensatory increases in nonoxidative glucose metabolism or explained by a reduction in total energy production.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".