Noninvasive Measurement Techniques for Monitoring of Microvascular Function in the Diabetic Foot

Abstract

There are, currently, 3 established clinical techniques routinely employed to determine the risk of ulceration in the diabetic foot. These are assessment of the circulation, the nervous control of sensation, and foot sensitivity to loading. Macrovascular measurements are used to assess sufficiency of the arterial supply to the foot. Evaluation of somatic neuropathy provides an indication of loss of plantar sensation. Skin pressure measurements indicate abnormalities in plantar loading. This combined approach is effective in allowing preventative measures to be applied prior to the onset of ulceration. In contrast, clinical measurement of microvascular function in the diabetic foot is uncommon. Indeed, there remains uncertainty regarding the importance of micro-vascular complications in the development of foot ulcers. This is in part due to the difficulty of making in vivo measurements of microvascular function. This article evaluates 3 noninvasive measurement techniques for routine micro-vascular assessment of the diabetic foot: transcutaneous oxygen tension, laser Doppler flowmetry, and near-infrared spectroscopy. These techniques can be used to obtain useful parameters of microvascular function including surface oxygen, blood flow, intracellular oxygenation, and cellular respiration. In principle, such measurements can be related to underlying pathophysiology, for example, microangiopathy or autonomic neuropathy. This article considers how these general techniques can be adapted to support routine clinical measurement of microvascular function, particularly in the neuropathic diabetic foot.