Comparative reproducibility of dermal microvascular blood flow changes in response to acetylcholine iontophoresis, hyperthermia and reactive hyperaemia.

Laser Doppler fluxmetry (LDF) can non-invasively measure skin microvascular changes in response to acetylcholine (ACh), local heating of the skin and reactive hyperaemia following arterial occlusion. Various studies have used microvascular changes in response to these stimuli, especially ACh iontophoresis and local heating, as a surrogate marker of endothelial function. There are few data in the literature regarding the comparative reproducibility of microvascular perfusion changes induced by the three stimuli. The aim of this study was to systematically assess and compare the reproducibility of skin microcirculatory function in response to each of these challenges. Ten healthy non-smoking subjects (seven males) median age 36 years (range 23-46), with no history of hypertension, diabetes, coronary artery disease or any connective tissue disorder, were studied. Changes in skin microcirculation in response to ACh iontophoresis, local heating of the skin and post-occlusive reactive hyperaemia, on two separate days (median 31, range 11-42 days), were assessed in all subjects. We measured three parameters: the change in perfusion from baseline perfusion (peak minus baseline perfusion), the relative percentage change in perfusion from baseline (peak--baseline)/baseline x 100 (%) and also the time-to-peak perfusion. The reproducibility of the change in perfusion had coefficients of variation (CV) of 9.3% for local skin heating, 19.4% for reactive hyperaemia and 25.5% for ACh iontophoresis. The relative percentage change in perfusion from baseline was more variable with CVs ranging from 23% to 39%. The coefficient of variation of time-to-peak perfusion was 7.0% for heating, 15.1% for reactive hyperaemia and 10.4% for ACh iontophoresis. We have shown that microcirculatory changes measured by the change in perfusion from baseline and time-to-peak perfusion in response to ACh, post-occlusive reactive hyperaemia and local skin heating had good reproducibility when carried out in a controlled environment with a standardized protocol. Relative change in perfusion had relatively poor reproducibility. The change in perfusion and time-to-peak perfusion for local skin heating were the most reproducible overall.