Reproducibility and methodological issues of skin post-occlusive and thermal hyperemia assessed by single-point laser Doppler flowmetry

Abstract

Objective The primary objective of this study was to evaluate 1-week reproducibility of post-occlusive reactive hyperemia (PORH) and local thermal hyperemia (LTH) assessed by single-point laser-Doppler flowmetry (LDF) on different skin sites. We also evaluated spatial reproducibility of both tests on the forearm. Finally, we assessed the influence of mental stress and room temperature variations on PORH and LTH. Methods We performed PORH and LTH assessing skin blood flow on the forearm and on the finger pad with LDF. We repeated the sequence 1 week later. We also performed PORH and LTH during mental stress (Stroop test) and at room temperatures of 21 °C and 27 °C. Data were expressed as cutaneous vascular conductance (CVC), as a function of baseline and as a function of 44 °C vasodilation (%CVC 44). Reproducibility was expressed as within subject coefficients of variation (CV) and intra-class correlation coefficients (ICC). Results Fourteen Caucasian healthy volunteers were recruited. Median age was 25 (2.7) and 50% were female. Median body mass index was 21.2 (5). PORH was reproducible on the finger, whether expressed as raw CVC (CV = 25%; ICC = 0.56) or as %CVC 44 (CV = 24%; ICC = 0.60). However, PORH showed poor reproducibility on the forearm. In the same way, LTH was reproducible on the finger pad when expressed as CVC (CV = 17%; ICC = 0.81) but not on the forearm. Spatial reproducibility was poor on the forearm. Elevated room temperature (27 °C) affected PORH and LTH on the finger pad ( p < 0.05) but not on the forearm. Conclusion Single-point LDF is a reproducible technique to assess PORH and LTH on the finger pad when data are expressed as raw CVC or %CVC 44. On the forearm, however, it shows great inter-day variability, probably due to spatial variability of capillary density. These results highlight the need for alternative techniques on the forearm.