Challenging dynamic cerebral autoregulation across the physiological CO<sub>2</sub> spectrum: Influence of biological sex and cardiac cycle
Bibliographic record
Abstract
Abstract This study applied alterations in partial pressure of end‐tidal carbon dioxide () to challenge dynamic cerebral autoregulation (dCA) responses across the cardiac cycle in both biological sexes. A total of 20 participants (10 females and 10 males; aged 19–34 years) performed 4‐min bouts of repeated squat–stand manoeuvres (SSMs) at 0.05 and 0.10 Hz (randomized orders) with clamped at ∼40 mmHg. The protocol was repeated for hypercapnic (∼55 mmHg) and hypocapnic (∼20 mmHg) conditions. Middle cerebral artery (MCA) and posterior cerebral artery (PCA) were insonated via transcranial Doppler ultrasound. Dynamic end‐tidal forcing clamped , and finger photoplethysmography quantified beat‐to‐beat changes in blood pressure. Linear regressions were performed for transfer function analysis metrics including power spectrum densities, coherence, phase, gain and normalized gain (nGain) with adjustment for sex. During hypercapnic conditions, phase metrics were reduced from eucapnic levels (all P < 0.009), while phase increased during the hypocapnic stage during both 0.05 and 0.10 Hz SSMs (all P < 0.037). Sex differences were present with females displaying greater gain and nGain systole metrics during 0.10 Hz SSMs (all P < 0.041). Across stages, females displayed reduced buffering against systolic aspects of the cardiac cycle and augmented gain. Sex‐related variances in dCA could explain sex differences in the occurrence of clinical conditions such as orthostatic intolerance and stroke, though the effect of fluctuating sex hormones and contraceptive use on dCA metrics is not yet understood.
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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".