Reliability of Reflex Cutaneous Vasodilation on the Forearm Measured Using Laser‐Doppler Flowmetry During Whole‐body Passive Heating
Bibliographic record
Abstract
Laser‐Doppler flowmetry (LDF) quantifies changes in localized microvascular perfusion in response to thermal and non‐thermal stimuli. Despite its widespread use, the reliability of the measurement during whole‐body heating is unknown. This presents a key knowledge gap that is critical for experimental design, statistical analysis, and interpretation. The purpose of this study was therefore to assess the reliability of LDF‐derived cutaneous vasodilation between separate days ( between‐day ) and between forearm sites ( within‐day ) during incremental whole‐body heat stress. On three occasions (~1 week apart), 11 healthy men (25 [SD 5] years) were passively heated (whole‐body heating using a water perfused suit) to increase esophageal temperature (T eso ) by +0.7°C [0.11] (low heat stress, LHS) and +1.3°C [0.14] (moderate heat stress, MHS). Forearm skin blood flow (arbitrary perfusion units; PU) was measured in three adjacent sites on the mid‐dorsal forearm using LDF (Perimed) while local skin temperature was clamped (34°C). Maximal vasodilation was achieved by heating each skin site to 44°C (for ≥ 20 min), but without the use of SNP, while T eso was clamped at +1.8°C [0.1]. Beat‐to‐beat mean arterial pressure (MAP) was measured continuously. Cutaneous vascular conductance (CVC) at each skin site was calculated as PU/MAP. Data were presented as absolute CVC and percentage of maximal vasodilation (%CVC 44 ). Reliability was assessed at baseline (no heat stress, NHS), LHS, and MHS using the intra‐class correlation coefficient (ICC), with values ≥0.7 considered acceptable for research purposes. Between days, CVC increased from 0.3 [0.2] to 2.0 PU [0.8] at LHS, and then to 2.1 PU [0.8] at MHS. Expressed as %CVC 44 this equated to increases from 12 [5] to 68% [15] and then 73% [13]. Within‐day ( i.e. , between sites), average CVC increased from 0.3 [0.2] to 1.9 PU [0.7] at LHS, and 2.0 PU [0.7] at MHS, which related to an increase from 13 [6] to 71% [15] at LHS, and to 76% [12] at MHS when expressed as %CVC 44 . At NHS, the between‐ and within‐day reliability of these measurements did not exceed the 0.7 ICC threshold when expressed as CVC or %CVC 44 at NHS (range: 0.00 to 0.45). Similarly, at LHS and MHS the between‐day reliability did not exceed 0.7 when expressed as CVC (0.57 and 0.69, respectively) or %CVC 44 (both 0.57). While within‐day reliability of %CVC 44 at LHS and MHS was not acceptable (0.54 and 0.64, respectively), it was when expressed as CVC (0.74 and 0.71, respectively). We show that the between‐day reliability of this technique was poor, irrespective of the level of whole‐body heat stress, but within‐day reliability was acceptable during heating, but not for resting measurements. This has important implications for studies assessing reactivity of skin vasculature to passive whole‐body hyperthermia, particularly with respect to the expected difference between the signal ( i.e. , expected change) and noise ( i.e. , measurement and biological variability), and the need to ensure that repeated measurements reflect the same microvascular environment. Support or Funding Information Natural Sciences and Engineering Research Council of Canada
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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 | 0.004 |
| 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".