Reproducibility of skin microcirculatory measurements in humans, with special emphasis on capillaroscopy

The reproducibility of capillaroscopic measurements of capillary blood cell velocity (CBV) in human nailfolds was investigated by use of the computerized system CapiFlow. Therefore, CBV measurements of two capillaries of each of three fingers together with laser Doppler fluxmetry (LDF) and skin temperature measurements were performed three times in five healthy volunteers. Short-term (1.5 h) intra-individual coefficient of variation (CV) of CBV was 18.4%. Long-term (7 days) CV amounted to 55.8%. Inter-individual CV was 55.9%. Short- and long-term intra-individual CVs of LDF were 25.4% and 37.3%. Inter-individual variation was 36.0%. Skin temperature showed short- and long-term CVs of 3.7% and 5.5% and inter-individual CV of 5.8%. In conclusion, measurement of CBV using CapiFlow is a suitable method to assess acute effects, but has limited value in investigating long-term effects. Because of the wide interindividual variability in both CBV and LDF, power calculations will reveal large numbers to investigate. Skin temperature has a relatively small intra- and inter-individual variation and is more suitable for long-term studies.