Comparison of baroreflex sensitivity gain during mild lower body negative pressure in presence and absence of long duration bed rest
Bibliographic record
Abstract
Lower body negative pressure (LBNP) and head down bed rest (HDBR) are protocols used to simulate hypovolemia and cardiovascular deconditioning, causing an alteration of autonomic control of circulation. The objective of this study was to investigate the combined effects of LBNP and bed rest on cardiac baroreflex sensitivity (BRS). RR and systolic blood pressure (SBP) recordings from seven volunteers were analyzed during a mild LBNP protocol consisting of three different levels of LBNP (-10 mmHg, -20 mmHg, -30 mmHg) before (pre-HDBR) and on day 50 of a HDBR study. Spectra of RR and SBP were computed and BRS was assessed in the low frequency (LF) and high frequency (HF) bands through a bivariate model that takes into account the causal relationships between heart rate (HR) and arterial blood pressure. HR significantly increased from BL in HDBR for LBNP≤-20 mmHg. BRS gain decreased significantly in the LF band with increasing levels of LBNP in both conditions. BRS gain was significantly lower on day 50 of HDBR with respect to pre-HDBR at -20 mmHg. These data suggest that BRS in the LF range is reduced in bed rest, and these changes may be due primarily to a reduction in plasma volume associated with bed rest, which impact the physiological responses of autonomic control of circulation.
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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".