Middle cerebral artery mean flow velocity changes to non‐pharmacologically induced hypertension and hypotension in humans (1184.6)
Bibliographic record
Abstract
Asymmetrical responses of cerebral blood flow in response to elevating vs. falling blood pressure has been reported using cyclic inflation and deflation of thigh cuffs in head injury patients and pharmacologically in healthy volunteers. Whether this phenomenon exists with non‐pharmacologically induced hypertension and hypotension is unknown. In this study, we examined the relative changes in cerebrovascular conductance index (CVCi), defined as percent changes in middle cerebral artery mean flow velocity / percent changes in mean arterial pressure, during transient hypertension vs. hypotension in 10 healthy male volunteers {age [median (range)]: 24 (22‐35 yrs), body weight [mean±SD: 72±12 kg]; maximal oxygen uptake: 55±5 ml/kg/min}. Transient hypertension and hypotension were induced via squat‐stand manoeuvres executed at 0.025, 0.05 and 0.1 Hz. The CVCi responses to hypertension (squat) compared to hypotension (stand) were attenuated at 0.05 Hz (0.57±0.38 vs. 1.84±0.56 %/%) and 0.1 Hz [0.83±0.41 vs. 1.59±0.57 %/%; all p<0.01), but not at 0.025 Hz [0.86±0.30 vs. 1.12±0.31 %/%; p=0.1). These results suggest that the human cerebrovascular function is better adapted to combat non‐pharmacologically and physiologically relevant transient hypertension than transient hypotension. Grant Funding Source : Supported by a research contract from the Ministère de l’Éducation, du Loisir et du Sport (Québec)
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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 | 0.001 |
| 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) | 0.001 | 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".