The Magnitude of FMD is Determined by the Area Under the Curve of the Reactive Hyperemia
Bibliographic record
Abstract
The reactive hyperemia (RH) test commonly used to assess flow mediated dilation (FMD) in human conduit arteries creates a large, transient shear stimulus. PURPOSE: To identify the relative importance of the peak vs. the duration of shear rate in determining the peak FMD response. METHODS: Brachial artery (BA) blood flow velocity was measured with Doppler ultrasound and echo ultrasound BA images were analyzed with automated edge detection software (shear rate = velocity/diameter). 1) Duration manipulation experiment (DME) - 10 healthy males underwent six RH trials with different hyperemic durations (10s–2 min). The duration of hyperemia was manipulated by re-inflating the occlusion cuff after 10s, 20s, 30s, 40s, or 50s. 2) Peak manipulation experiment (PME) - 8 healthy males underwent three RH trials. Three peak shear rate magnitudes (large (L), medium (M) and small (S)) were created by applying BA compression upon cuff release. The post-peak area under the curve (AUC) of shear rate was also controlled with arterial compression. RESULTS: DME - Peak shear rate (AUC in 1st 9s post cuff release) was not different between trials (P = 0.309). Re-inflation of the occlusion cuff at times indicated resulted in the remaining AUC being significantly different between trials (10 s −2025.37 ±504.21; 20 s −3393.54±857.03; 30s-4329.30±1198.47; 40s–4784.20±1345.00; 50s–5215.83±1466.63 2min −7124.39±2160.67 p<0.001). The respective peak % changes in diameter were: 10s-2.67±1.34; 20s-6.21±1.95; 30s-7.89±2.95; 40s-8.3±3.21; 50s-7.91±3.20; 2min-9.34±4.10, with 10 and 20 s being significantly less than 2min (p<0.001). PME - Peak shear rate (AUC in 1st 9s post cuff release) was significantly different between trials (L- 998.04±305.16, M-700.66±225.89, S-487.48±1 67.55 p<0.001). The AUC of the post-peak shear rate was not significantly different between trials (P = 0.695). The peak % change in diameter was not significantly different between trials (L-6.99±2.72%, M-7.56±2.6%, S-6.87±1.99%, P = 0.437). CONCLUSIONS: Manipulation of the duration of the shear rate had an impact on the peak FMD response while independent manipulation of peak shear rate did not. We conclude that the shear rate AUC following the peak is a critical determinant of the peak FMD response and needs to be accounted for in quantifying the stimulus for FMD. Supported by ACSM Doctoral Research Grant, NSERC, CFI New Opportunities Fund
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".