Variability in skin microvascular vasodilatory responses assessed by laser-Doppler imaging

Skin blood perfusion (SBP) responses to pressure loading and other traumatic and noxious stimuli are used to help identify patients at-risk of skin breakdown, evaluate preventive strategies and help clarify patho-physiological mechanisms in pre-ulcerative and ulcerative conditions. Often, laser-Doppler methods are used to compare vasodilatory responses at differing skin sites to evaluate skin parameter changes. Significant variations in skin microvasculature are known to be normally present, even in closely separated skin zones. In this study, spatial variability and temporal responses of SBP were evaluated with a widely used topical vasodilator (methylnicotinate, MN). A mask with nine holes (1.25 cm2 each) was placed on the volar forearm of ten volunteers. SBP was measured with laser-Doppler Imaging (LDI) prior to applying MN (15 ul, 50 mM) to six zones and 5, 10, 15, 20 and 30 minutes afterwards. Inter-zone mean SBP and inter- and intra-zone coefficients of variation (CV) were determined at each time. Results show that MN responses, when determined as zone LDI means, reached maximum at 15 minutes with no significant differences in relative responses among treated zones. Inter-zone perfusion CV's (range 0.11-0.13) were about 50 percent of intra-zone CV's (p < 0.01). We conclude that LDI perfusion responses can be obtained at different forearm skin sites with reasonable and acceptable levels of spatial variation if zone mean SBP values are used.