Autonomic compensation to simulated hemorrhage monitored with heart period variability
Bibliographic record
Abstract
OBJECTIVE: To test the hypothesis that components of heart period variability track autonomic function during simulated hemorrhage in humans. DESIGN: Prospective experimental laboratory intervention. SETTING: Human physiology laboratory. SUBJECTS: A total of 33 healthy, nonsmoking, volunteer subjects (23 men, ten women). INTERVENTIONS: Progressive lower body negative pressure was applied in 5-min stages until the onset of impending cardiovascular collapse. MEASUREMENTS AND MAIN RESULTS: The electrocardiogram, beat-by-beat finger arterial pressure, and muscle sympathetic nerve activity from the peroneal nerve were recorded continuously. Pulse pressure was calculated from the arterial pressure waveform and used as an estimate of relative changes of central blood volume. Heart period variability was assessed in both time and frequency domains. Application of lower body negative pressure caused progressive reductions of R-R interval and pulse pressure and progressive increases of muscle sympathetic nerve activity. Arterial pressures changed minimally and late. R-R interval time domain variability measures and spectral power at the high frequency (0.15-0.4 Hz) decreased progressively with lower body negative pressure (p < .001). Both R-R interval high-frequency power and time domain variability measures correlated inversely with muscle sympathetic nerve activity and directly with pulse pressure (all amalgamated R2 > .88, all p < or = .001). CONCLUSIONS: Components of heart period variability track early compensatory autonomic and hemodynamic responses to progressive reduction in central blood volume. Such analyses, interpreted in conjunction with standard vital signs, may contribute to earlier assessments of the magnitude of blood volume loss during hemorrhage.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 |
| 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".