Cardiovascular re-adjustments and baroreflex response during clinical reambulation procedure at the end of 35-day bed rest in humans
Bibliographic record
Abstract
During the reambulation procedure after 35-day head-down tilt bed rest (HDTBR) for 9 men, we recorded for the first time heart rate (HR; with electrocardiogram) and arterial pressure profiles (fingertip plethysmography) for 5 min in HDTBR and horizontal (SUP) positions, followed by 12 min in standing position, during which 4 subjects fainted (intolerant, INT) and were laid horizontal again (Recovery). We computed: mean arterial pressure (P̄; pressure profiles integral mean), stroke volume (SV; obtained with Modelflow method), and cardiac output (Q̇; SV × HR). All cardiovascular data remained stable in HDTBR and SUP for both groups (EXP). Taking the upright posture, EXP showed a decrease in SV and an increase in HR, becoming significantly different from SUP within 1 min. Further evolution of these parameters kept Q̇ stable in both groups until the second minute of standing. Afterward, in INT, P̄ precipitated without further HR increases: SV stopped being corrected and Q̇ reached 2.9 ± 0.4 L·min(-1) at the last 15 s of standing. Sudden drop in P̄ allowed identification of a low-pressure threshold in INT (70.7 ± 12.9 mm Hg), after which syncope occurred within 80 s. During Recovery, baroreflex curves showed a flat phase (P̄ increase, HR stable), followed by a steep phase (P̄ increased, HR decreased, starting when P̄ was 84.5 ± 12.5 mm Hg and Q̇ was 9.6 ± 1.5 L·min(-1)). INT, in contrast with tolerant subjects, did not sustain standing because HR was unable to correct for the P̄ drop. These results indicate a major role for impaired arterial baroreflexes in the onset of orthostatic intolerance.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".