A Portable Heat-Exchange-Based System for Assessing Digital Vascular Response to Cold

Background: Digital vascular assessment is relevant in occupational medicine, but current measurement methods may be complex and poorly portable. Objective: To validate a portable heat-exchange-based system for assessing cold-induced digital vascular response, using strain-gauge plethysmography as the reference method. Methods: Twenty healthy volunteers, 10 males and 10 females, underwent five subsequent sessions. Finger blood flow (FBF) was assessed by strain-gauge plethysmography, while simultaneously, fingertip thermal power (TP) was recorded with a portable thermoflowmeter. FBF was measured at baseline, while both FBF and TP were measured during application of 1-N contact force alone and during 1-N force combined with local cooling at 10 °C. The relationship between TP and FBF, after adjustment for covariates (age, sex, body mass index (BMI), and room temperature), was evaluated in the cooled condition using a linear mixed model including fixed and random effects. Results: Local cooling induced a significant vascular response, with FBF decreasing from 1.23 to 0.98 ml/100 ml/s (p<0.0001). In the cooled-condition model, TP was significantly associated with FBF, with each 1 ml/100ml/s increase in FBF corresponding to a 39.6 mW increase in TP (p<0.0001). Under cooling, TP showed lower within-subject variability than FBF (wsCV ≈0.19 vs ≈0.64). BMI was positively associated with TP (4.40 mW per kg/m², p=0.007), whereas age and sex were not significant predictors. Conclusions: These findings support the interpretation of TP as a perfusion-related thermal descriptor with potential applicability in occupational health surveillance. Further validation in subjects with digital vascular disorders is needed.