Body position does not affect respiratory sinus arrhythmia magnitude (1103.4)
Bibliographic record
Abstract
Body position does not affect respiratory sinus arrhythmia magnitude Respiratory sinus arrhythmia (RSA) is the normal fluctuation in heart rate in phase with respiration. Instantaneous heart rate (IHR) increases with inspiration and decreases with expiration. The mechanisms underlying RSA are unclear, but some evidence suggests that central brainstem mechanisms drive RSA, independent of afferent feedback. Cardiac loading associated with inspiration or gravity may also trigger the Bainbridge reflex, although the contribution of this reflex is unclear in humans. We investigated the effects of incremental increases in inspired volume on RSA magnitude during both 45° head‐up and head‐down tilt (HUT, HDT). Six healthy subjects were positioned on a tilt table and instrumented with ECG to measure IHR (60/period) and a pnuemotachometer to measure respiratory volumes. Following a forced vital capacity (FVC) measurement, subjects were coached to breathe 30 consecutive breaths at each inspiratory volume of 10, 15, 20, 25 and 30% of FVC using a computer screen for visual feedback. The average RSA magnitude of the middle 10 breaths of each trial was plotted against the inspired volume, and linear regression was performed. The increase in RSA magnitude with inspired volume was highly linear in HUT and HDT (R 2 >0.9), but the mean slopes were not different between positions. We have determined a range of inspired volumes that generate a linear RSA magnitude response. Further, our data demonstrate that gravity‐dependent cardiac loading does not influence RSA magnitude associated with increases in inspired volume.
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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) | 0.006 | 0.001 |
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".