Temporal and spatiotemporal variability in comprehensive forearm skin microcirculation assessment during occlusion protocols.

Forearm skin hyperemia during release after brachial occlusion has been proposed for evaluating peripheral arterial disease and endothelial dysfunction. We used a novel fiberoptic system integrating Laser Doppler Flowmetry and Diffuse Reflectance Spectroscopy for a comprehensive pointwise model based microcirculation characterization. The aim was to evaluate and compare the temporal and the spatiotemporal variabilities in forearm skin microcirculation parameters (speed resolved perfusion; low speed <1mm/s, Perf; mid-speed 1-10mm/s, high speed >10mm/s, and total perfusion (Perf); the concentration and oxygenation of red blood cells, C and S). Ten healthy subjects underwent arterial and venous forearm occlusions (AO, VO), repeated within one week. The repeatability was calculated as the coefficient of variation (CV) and the agreement as the intra-class correlation coefficient (ICC). The temporal CVs for conventional perfusion, Perf, Perf, C and S were 14%, 12%, 9% and 9%, respectively, while the ICC were >0.75 (excellent). The perfusion measures generally had a higher spatiotemporal than temporal variability, which was not the case for S and C. The corresponding spatiotemporal CVs were 33%, 32%, 18% and 15%, respectively. During VO, C had a CV<35% and ICC>0.40 (fair-good), and after release this was the case for C (AO and VO), S (VO) and Perf (VO). In conclusion, the skin microcirculation parameters showed excellent temporal repeatability, while the spatiotemporal repeatability especially for perfusion was poorer. The parameters with acceptable repeatability and fair-good agreement were: C during and after release of VO, the Perf after release of VO, the S and the C after release of AO. However, the value of these parameters in discriminating endothelial function remains to be studied.