Standard and Near-Surface Laser-Doppler Perfusion in Foot Dorsum Skin of Diabetic and Nondiabetic Subjects with and without Coexisting Peripheral Arterial Disease

Abstract

Appropriate assessment of microvascular function is now recognized as an important adjunct to the diagnostic workup and medical follow-up for a variety of conditions. Laser Doppler fluxmetry (LDF)-derived rbc perfusion (Q) and the volume (V) and velocity (U) components are useful in this regard but the fact that the sampled volume includes both nutritional and nonnutritional components may limit its specificity and range of usefulness. It was reasoned that if the depth of penetration could be reduced without significantly altering essential optical transmission features, then the detected signal would better represent the nutritional component. A 0.68-mm-thick Delrin spacer was fabricated and used to compare LDF values with (WITH) and without (WITHOUT) its use on the foot dorsum of 71 limbs of 44 diabetic (DM) and nondiabetic (NO-DM) subjects with lower extremity arterial disease (LEAD, n = 39) and without disease (NORM, n = 32). Overall LDF values WITH as compared to WITHOUT had a slightly greater U (1.01 vs 0.89 mm/sec, P < 0.01) and much lower V (0.06 vs 0.63%, P < 0.001) and Q (0.25 vs 1.88 ml/min/100 g, P < 0.001). In NO-DM subjects, WITH detected a lower Q in limbs with LEAD (0.14 vs 0.27, P < 0.05) but WITHOUT did not (1.48 vs 1.47, ns). In DM subjects, WITH measured a significantly lower U in LEAD limbs (1.05 vs 1.22 mm/sec, P < 0.05), which was not detected WITHOUT. Without the spacer, NORM limb LDF values were all greater in DM vs NO-DM subjects. With spacer use, only the DM velocity component was significantly greater. Use of a modified LDF procedure has shown both utility and promise as a method for evaluation of skin microcirculation and appears to offer some potential benefits as compared with the currently used standard method. Previously undocumented differences between LEAD and NORM limbs in DM and NO-DM patients as herein reported represent initial findings using a 0.68-mm spacer.