Interrelationships between pulse arrival time and arterial blood pressure during postural transitions before and after spaceflight
Bibliographic record
Abstract
We tested the hypothesis that acute changes in arterial blood pressure (BP) when astronauts moved between supine and standing posture before and after spaceflight can be tracked by beat-to-beat changes in pulse arrival time (PAT). Nine male crewmembers (45 ± 7 yr of age; mean mission length: 165 ± 13 days) participated in a standardized supine-to-sit-to-stand test (5 min-30 s-3 min) before flight and 1 day following return to Earth with continuous monitoring of ECG and finger arterial BP. PAT was determined from the R-wave of the ECG to the foot of the BP waveform. On average, modest cardiovascular deconditioning was detected by ~10 beats/min increase in heart rate in supine and standing posture after spaceflight ( P < 0.05). When looking across the full data collection period, the r2 values between inverse of PAT (1/PAT) and systolic (SBP) and diastolic BP (DBP) varied considerably between individuals (SBP preflight 0.142 ± 0.186, postflight 0.262 ± 0.243). Individual variability was consistent during periods of transition (SBP preflight 0.284 ± 0.324, postflight 0.297 ± 0.269); however, when SBP dropped >20 mmHg, r2 was significant in 5 of 5 preflight tests and 5 of 7 postflight tests. The standard error of the estimate based on a simple linear model during both pre- and postflight testing was 9–11 mmHg for SBP and 6–7 mmHg for DBP. Overall, the results support the hypothesis that PAT tracked dynamic changes in BP. PAT as a noninvasive, nonintrusive surrogate for changes in BP could be developed as an indicator of risk for syncope on return from spaceflight or other Earth-based applications. NEW & NOTEWORTHY Astronauts returning to Earth’s gravity are at increased risk of low blood pressure on standing. Arterial pulse arrival time tracked the decrease in arterial blood pressure on moving from supine to upright posture. Nonintrusive technology providing indicators sensitive to acute changes in blood pressure could act as an early warning system to identify risk for hypotension that place astronauts, or people on Earth, at risk of impaired cognitive performance, fainting, and falls.
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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 | 0.002 |
| 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".