Differences between middle cerebral artery blood velocity waveforms of young and postmenopausal women
Bibliographic record
Abstract
In Brief Objective: We characterized middle cerebral artery (MCA) blood flow velocity waveforms measured by transcranial Doppler ultrasonography in premenopausal (26.6 ± 6.1 years, mean ± SD) and postmenopausal (54.0 ± 3.6 years) women, of whom six were receiving hormone therapy (PM-HT) and seven were not (PM-non-HT). We hypothesized that feature points on MCA waveforms are altered in postmenopausal women compared with those in young women. Design: A short protocol involved maintaining end-tidal PO2 at euoxia (88 mm Hg) and end-tidal PCO2 at 1.5 mm Hg above eucapnic values using a dynamic end-tidal forcing system. Doppler data for the velocity spectral outline (Vp) were collected every 10 ms, and velocity waveform analyses were done on a beat-by-beat basis. Waveform features were identified over each cardiac cycle, including the average Vp (VCYC), maximum acceleration (AMAX), and the ratio of the velocity at the reflected wave and the velocity at peak systole (VR:VMAX). Results: VCYC was unchanged between premenopausal and postmenopausal women (69.4 ± 9.6 and 67.5 ± 11.1 cm/s, respectively). AMAX was significantly higher (P = 0.007) in premenopausal women (987.9 ± 280.7 cm/s2) compared with postmenopausal women (743.1 ± 100.3). Conversely, VR:VMAX was significantly smaller (P < 0.001) in premenopausal women (0.90 ± 0.09) compared with postmenopausal women (1.11 ± 0.05). In postmenopausal women, the reflected wave is higher than the maximum velocity at peak systole, suggesting the presence of a shoulder in the MCA waveform. Conclusions: Further investigations are required to assess whether this waveform analysis can provide insight into pathophysiologic changes in cerebral hemodynamics with aging. This study used a technique of waveform analysis to identify several feature points on middle cerebral artery blood flow velocity waveforms measured by transcranial Doppler ultrasonography in premenopausal and postmenopausal women. In the postmenopausal women, the reflected wave that occurs after systole was higher than the maximum velocity at peak systole, suggesting the presence of a shoulder in the reflected velocity waveform.
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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".