Directional Sensitivity Of Dynamic Cerebral Autoregulation In Healthy Lowlanders At High Altitude And High Altitude Natives
Bibliographic record
Abstract
INTRODUCTION: Dynamic cerebral autoregulation (dCA), quantified via transfer function analysis with repeated squat-stands (RSS), is unaltered throughout high-altitude (HA, 5,050 m) partial acclimatization (2 weeks) in lowlanders (LL) and HA natives. Directional sensitivity of the dCA response (i.e., the attenuated change in cerebral blood velocity when mean arterial pressure [MAP] transiently increases vs. decreases) is reported at sea level. Whether the dCA response directional sensitivity is altered in LL at HA or differs from HA natives is unknown. OBJECTIVE: To examine the dCA directional sensitivity responses in healthy LL at HA and HA natives. METHODS: MAP and middle cerebral artery mean blood velocity (MCAv) were recorded continuously during 5-min RSS at 0.05 Hz and 0.10 Hz at sea level (N = 10, 29 ± 7 yrs), initial exposure to 5,050 m (N = 8, 28 ± 5 yrs), after 2 weeks of acclimatization to HA (N = 9, 29 ± 7 yrs), and in HA natives at HA (5,050 m; N = 16, 32 ± 14 yrs). For each transition, we calculated absolute MCAv and MAP changes with respect to the transition time intervals of both variables indexing time adjusted ratios when MAP increases (ΔMCAvT/ΔMAPTINC ) and decreases (ΔMCAvT/ΔMAPTDEC ). Values were then averaged over the 5-min RSS. RESULTS: In LL, ΔMCAvT/ΔMAPTINC was lower than ΔMCAvT/ΔMAPTDEC at sea level, initial arrival to HA, and after 2 weeks of HA acclimatization at both 0.05 Hz (MAP direction: p = 0.028, condition: p = 0.598, interaction: p = 0.181) and 0.10 Hz RSS (MAP direction: p = 0.002, condition: p = 0.547, interaction: p = 0.204). When acclimatized LL were compared with HA natives, ΔMCAvT/MAPTINC was lower than ΔMCAvT/ΔMAPTDEC at 0.05 Hz (MAP direction: p = 0.001, condition: p = 0.213, interaction: p = 0.601), while ΔMCAvT/ΔMAPTINC and ΔMCAvT/ΔMAPTDEC were not different at 0.10 Hz RSS (MAP direction: p = 0.547, condition: p = 0.117, interaction: p = 0.823). CONCLUSION: Directional sensitivity of dCA is present at both 0.05 Hz and 0.10 Hz in LL at sea level. Acute HA exposure and 2 weeks of partial HA acclimatization does not appear to have an influence on the dCA directional sensitivity. In addition, dCA directional sensitivity in HA natives is not different than partially acclimatized LL. Further research is needed to understand whether atmospheric pressure and carbon dioxide could influence these findings.
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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 | 0.000 |
| 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".