Influence of sex, menstrual cycle, and oral contraceptives on cerebrovascular resistance and cardiorespiratory function during Valsalva or standing
Bibliographic record
Abstract
Women experience orthostatic intolerance more than men, and they experience faintness more in the early follicular [i.e., low-hormone (LH)] than luteal [i.e., high-hormone (HH)] phase of the menstrual cycle. Men ( n = 13, 25.8 ± 1.8 yr old) and women in the LH ( days 2–5; placebo) and HH ( days 18–24; high dose) phases of the menstrual cycle with (OC; n = 14, 22.0 ± 0.8 yr old) or without (NOC; n = 12, 21.8 ± 0.5 yr old) oral contraceptive (OC) use underwent the Valsalva maneuver and a supine-sit-stand protocol. Blood pressure, normalized stroke volume [stroke volume index (SVi)], cardiac output index, heart rate, end-tidal CO 2 , and middle cerebral artery (MCA) blood flow velocity were measured. When subjected to the Valsalva maneuver, all women had a greater increase in diastolic and mean MCA blood flow velocity than men ( P ≤ 0.065), with no significant effect of menstrual cycle phase or OC use. When subjected to the supine-sit-stand protocol, men had lower MCA blood flow velocity ( P < 0.038) than all women, and SVi was higher in men than in the NOC group in all postures ( P < 0.011) and in the OC group in the LH phase of the menstrual cycle during standing ( P = 0.010). Only men experienced higher resistance index ( P < 0.001) and pulsatility index ( P < 0.001) with standing. The OC group had lower end-tidal CO 2 ( P = 0.002) than the NOC group ( P = 0.030) and men ( P ≤ 0.067). SVi ( P = 0.004) and cardiac output index ( P = 0.008) were higher in the OC than NOC group. A tendency toward a lower mean MCA blood flow velocity ( P = 0.058) and higher SVi ( P = 0.059) and pulsatility index ( P = 0.058) was noted in the HH than LH phase. Mean arterial pressure was higher in the OC than NOC group in the LH phase ( P = 0.049) and lower in the HH than LH phase ( P = 0.014). Our results indicate that cycling estrogens/progestins can influence ventilatory, cardiovascular, and/or cerebrovascular physiology. NEW & NOTEWORTHY We have found sex differences in the cerebrovascular response to the Valsalva maneuver and standing. Men have greater cerebral vasoconstriction (or women have greater cerebral vasodilation) during late phase II of the Valsalva maneuver, and the cerebrovascular resistance index increases in men, but not in women, during standing. Furthermore, our findings indicate that both the menstrual cycle phase and oral contraceptive use can influence cardiovascular function both at rest and during active standing.
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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) | 0.002 | 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".