Comparison of the effects of independently‐controlled end‐tidal PCO<sub>2</sub> and PO<sub>2</sub> on blood oxygen level–dependent (BOLD) MRI
Bibliographic record
Abstract
PURPOSE: To assess the effect of changes in end-tidal partial pressure of O(2) (PETO(2)) on cerebrovascular reactivity (CVR) estimated from changes in blood oxygen level-dependent (BOLD) signal during cyclic changes in end-tidal partial pressure of CO(2) (PETCO(2)). MATERIALS AND METHODS: BOLD response to fixed cyclic step changes in PETCO(2) (range = 30.4-48.8 mmHg) and PETO(2) (range = 100.6-444.0 mmHg) was studied in four healthy volunteers. RESULTS: The BOLD reactivity to PETCO(2) and PETO(2) were 0.283 (0.188-0.379) (median, range) and 0.004 (0.003-0.006)%/mmHg, respectively, in the whole brain; 0.438 (0.382-0.614) vs. 0.006 (0.004-0.009)%/mmHg, respectively, in the gray matter; and 0.075 (0.065-0.093) vs. 0.002 (0.001-0.002)%/mmHg, respectively, in the white matter. CONCLUSION: The BOLD reactivity to PETO(2) was much smaller than that to PETCO(2). However, BOLD reactivity can be significantly distorted by CO(2)-induced changes in PETO(2). We conclude that PETO(2) should be carefully controlled during studies that use BOLD reactivity as an indicator of CVR.
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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 | 0.002 |
| 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 | 0.001 |
| 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".