Visualizing and quantifying the impact of reactive hyperemia on cutaneous microvessels in humans
Bibliographic record
Abstract
The mechanisms underlying reactive hyperemia (RH) responses in microvessels are poorly understood. Previous assessment tools have not been capable of directly visualizing microvessels during physiological stimulation in humans. Optical coherence tomography (OCT) is capable of imaging and quantifying subcutaneous microvessels as small as ~30 µm. In this study we use OCT to visualize and quantify skin microvascular changes in response to RH for the first time in humans. We also assessed the reproducibility of this technique. OCT and laser Doppler flowmetry (LDF) were used simultaneously to scan cutaneous microvessels in 10 young healthy subjects on 2 days. We applied a speckle decorrelation algorithm to assess OCT images and calculated flow rate, speed, diameter, and density parameters. Measures were obtained at rest (baseline) and 30-s following a 5-min cuff inflation (RH). All data were compared between days. The RH stimulus significantly increased ( P < 0.0001) OCT-derived microvascular diameter (37.6 ± 3.4 vs. 44.5 ± 5.2 µm), flow rate (82.4 ± 23.4 vs. 240.1 ± 58.6 pl/s), speed (48 ± 5.7 vs. 101.5 ± 17.1 µm/s), density (5.1 ± 1.7 vs. 14.6 ± 2.6%), and also LDF-derived flux (12.3 ± 5.7 vs. 31.6 ± 9.1 perfusion units). At baseline, OCT-derived diameter ( r = 0.55), flow rate ( r = 0.64), speed ( r = 0.55), and density ( r = 0.75) showed significant between-day correlations ( P < 0.05), as did LDF results ( r = 0.74). In response to RH, OCT-derived diameter ( r = 0.63) and density ( r = 0.64) showed significant correlations ( P < 0.05), whereas flow rate ( r = 0.45), speed ( r = 0.43), and LDF ( r = 0.26) were less reproducible. Our study is novel in that it establishes the feasibility of using OCT to visualize and quantify microvascular structure and function responses to RH in humans. NEW & NOTEWORTHY This study describes the first evidence in humans that optical coherence tomography provides direct visualization and comprehensive quantification of cutaneous microvascular hemodynamics as a response to reactive hyperemia. This imaging technique will greatly improve human cutaneous microvascular assessment in physiological and clinical settings.
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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 | 0.001 |
| 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".