Dynamic cerebral autoregulation during and following acute hypoxia: role of carbon dioxide
Bibliographic record
Abstract
Previous research has shown an inconsistent effect of hypoxia on dynamic cerebral autoregulation (dCA), which may be explained by concurrent CO2 control. To test the hypothesis that hypoxic dCA is mediated by CO2, we assessed dCA (transcranial Doppler) during and following acute normobaric isocapnic and poikilocapnic hypoxic exposures. On 2 separate days, the squat-stand maneuver was used to determine dCA in healthy subjects (n = 8; 3 women) in isocapnic and poikilocapnic hypoxia exposures (end-tidal oxygen pressure 50 Torr for 20 min). In isocapnic hypoxia, the amplitude of the cerebral blood flow response to increases and decreases in mean arterial blood pressure were elevated (i.e., increases in gain of +35 and +28%, respectively; P < 0.05). However, dCA gain to increases in pressure was reduced compared with baseline (-32%, P < 0.05) following the isocapnic hypoxia exposure. Similarly, intravenous bolus injections of sodium nitroprusside and phenylephrine in a separate group of subjects (n = 8; 4 women) also demonstrated a reduction in dCA gain to hypertension following isocapnic hypoxia. In contrast, dCA gain with the squat-stand maneuver did not significantly change from baseline during or following poikilocapnic hypoxia (P > 0.05). Our results demonstrate that dCA impairment in isocapnic hypoxia can be prevented with hypocapnia, and highlight the integrated nature of hypoxic cerebrovascular control, which is under strong CO2 influence.
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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) | 0.000 | 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 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".