Impaired cerebrovascular autoregulation and CO2 response are related to changes in systolic pressure after long‐duration spaceflight
Bibliographic record
Abstract
Intracranial hypertension has been identified as a risk for long‐duration spaceflight. We monitored changes in cerebral blood flow velocity (CBFV) in response to changes in blood pressure (autoregulation) and CO2 before and after spaceflight (147±49 days) in 5 men and 1 woman to determine if changes in CBFV or cerebrovascular resistance index (CVRi) related to changes in systolic blood pressure (SBP). Autoregulation and CO2 reactivity were measured during a test where two breaths of 10% CO2 were given 4 times during a 5min period. The autoregulatory index of the CVRi response to BP was reduced post‐flight (0.035±0.007 to 0.029±0.005, p<0.05) with a trend to a greater CBFV response to a change in BP (p=0.128). The post‐flight CVRi response to CO2 was significantly reduced (−0.038±0.018 to −0.028±0.012, p<0.05) with a simultaneous reduction in the CBFV response to CO2 (p=0.056). The change in SBP from pre‐ to post‐flight was correlated with the change in CBFV per mmHg change in BP (r=0.66) and the change in CBFV per mmHg change in CO2 (r=0.71). Individuals with elevated post‐flight SBP were more likely to have impairment of autoregulation and of cerebrovascular health as indicated by CO2 reactivity. With short‐flights no impairment was found in non‐syncopal astronauts; it is unknown if sustained intracranial hypertension and/or elevated environmental CO2 contributed to these changes. Funded by Canadian Space Agency.
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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".