Comparing The Dynamic Response Characteristics Of Flow-mediated Dilation In The Brachial And Radial Arteries
Bibliographic record
Abstract
Recent research indicates that smaller arteries tend to dilate more when exposed to shear stress (flow mediated dilation (FMD)) vs. larger arteries. However, the dynamic characteristics of FMD have not been compared in differently sized vessels. PURPOSE: To compare the Phase 1 (initial dilation) dynamics of the FMD response in the radial artery (RA) and the brachial artery (BA). METHODS: N = 15 healthy male subjects. BA and RA diameter and mean blood flow velocity (MBV) were measured by echo and Doppler ultrasound respectively. Rhythmic handgrip exercise was used to create a shear rate (shear rate (SR) estimate of shear stress = vessel diameter/MBV) of 60 s-1 for 6 minutes in the BA and RA. Subjects performed 3 exercise trials at the 60 s-1 SR target in each artery over three visits. These trials were averaged to provide one mean RA and one mean BA response. Curve fitting allowed determination of the phase 1 response dynamics (time delay (TD1) and time constant (tau 1)). Data are reported as means ± SD. RESULTS: RA diameter was 0.215 ± 0.0445 mm; BA diameter was 0.368 ± 0.0664 mm (P=0.002). The shear rate achieved in the RA (56.027 ± 3.935 s-1) and BA (57.939 ± 5.850 ss) was not significantly different (P = 0.120). The Phase 1 %FMD and %FMD at the end of the 6 min exercise bout were significantly greater in the RA (RA phase 1 = 6.25 ± 3.42%; 6 min 9.84 ± 3.99 %; BA 2.59 ± 1.69%; 6min 2.526 ± 1.96 %)(phase 1 P=0.005; 6min P=<0.001)). The RA had a significantly shorter TD1 (9.60 ±15.42 s) than BA (31.80 ± 26.15 s) (P = 0.017). However there was no significant difference in the speed of the phase 1 response (tau1) between the BA (51.30 ± 43.26 s) and RA (65.75 ± 38.40s) (P = 0.461). TD1 was modestly correlated with percent FMD in the RA (r2 = 0.146, P = 0.039) but not in the BA (r2 =.205, P = 0.104). Tau1 was not correlated with FMD in either the RA (P = 0.583) or the BA (P = 0.104). CONCLUSION: When experiencing a SR of 60 s-1, the RA began to dilate sooner (shorter TD1) and had a greater phase 1 %FMD magnitude than the BA. However, no differences could be detected in the speed of the phase 1 response (tau1). FMD response dynamics were largely unrelated to FMD magnitude. The distinct phase I FMD magnitudes and time delays in response to the same shear rate indicate vessel specific differences in the initiation of the FMD response. Supported by NSERC and CFI.
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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 | 0.001 | 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".