Cutaneous microvascular reactivity in the foot evaluated by optical multimodal pointwise and imaging techniques and different stimuli

Skin microvascular reactivity tests for the lower extremity apply stimuli such as ankle occlusion (post-occlusive reactive hyperemia, PORH), local heating (LH), or the vasoactive drug methyl nicotinate (MN). AIM: Evaluate microvascular reactivity in dorsal foot skin comparing PORH, LH and MN stimuli. METHOD: Thirty healthy participants 20-65 years of age were enrolled in a protocol using pointwise and imaging optical techniques for perfusion and oxygen saturation. Mean values and between-subjects coefficient of variation (CV) for perfusion and oxygen saturation were compared. RESULTS: The PORH, LH and MN stimuli caused significant increases in oxygen saturation and perfusion from baseline values (p < 0.001). The oxygen saturation was higher during LH than during PORH (pointwise technique; mean 88.8% vs 79.7%; p < 0.001) and higher during MN than during PORH (imaging; 86.7% vs 77.2%; p < 0.001). Perfusion was higher during LH than during PORH (pointwise; 1.60%RBC × mm/s vs 0.53%RBC × mm/s; p < 0.001) and higher during MN than during PORH (imaging; 1.04%RBC × mm/s vs 0.54%RBC × mm/s; p < 0.001). The CV for oxygen saturation was 2.8% vs 6.3% (pointwise; LH and PORH) and 7.4% vs 6.0% (imaging; MN and PORH). Corresponding values for perfusion were >30%. CONCLUSION: The responses in oxygen saturation and perfusion were higher during MN and LH stimuli than for PORH. A few outliers were observed after MN with a slower and lower response. Microcirculatory oxygen saturation has a lower between-subjects variation than perfusion (CV 3-7% vs >30%) during PORH, LH and MN stimuli.