The utility of hyperspectral imaging in patients with chronic venous disorders

Abstract

ObjectiveThe underlying pathophysiology of lower limb changes in chronic venous disorders (CVD) may involve alteration in microcirculation and tissue oxygenation. Hyperspectral imaging (HSI) is a noninvasive tool that is used clinically to measure transcutaneous oxygenation in peripheral artery disease and diabetic foot disease. However, there has been little application in venous disease. The aim of this study was to determine if transcutaneous oxygenation in the lower limb, as measured by HSI, changes depending on the clinical component of the Clinical-Etiological-Anatomical-Pathophysiological (CEAP) classification in CVD. MethodsThis was an observational study of patients with CVD recruited from a vascular specialist clinic at a tertiary hospital from January 2020 to January 2021. Participants were allocated to eight groups according to the clinical component of CEAP classification of CVD. Baseline demographic and risk factor information were collected. Transcutaneous oxygenation was measured using HSI at seven sites around the foot and gaiter area in the supine and standing position. Participants rested supine for 15 minutes before the supine measurements and then stood for 15 minutes before the standing measurements. Tissue oxygenation was analyzed over a fixed circular surface area of 79 mm2 at the target location. Calculations of oxyhemoglobin level (artificial unit [AU]), deoxyhemoglobin level (AU), oxygen saturation (%), and temperature (°C) were obtained. The Northern Ethics Committee (18/NTA/78) approved this conduct of the study and participants signed written consent forms. ResultsThere were 94 participants (164 lower limbs) included in the study. The median age was 59 years and 59 participants (63%) were women. At all sites except the heel, deoxyhemoglobin measurements increased in the standing position compared with the supine position (P < .001). In the gaiter region, there was nearly a doubling in deoxyhemoglobin level at 5 cm above the medial malleolus (supine 43.88 AU vs standing 80.46 AU; P < .001) and 5 cm above the lateral malleolus (supine 46.33 AU vs standing 87.72 AU; P < .001). When measurements were stratified by clinical class of the CEAP classification, there was a greater increase in deoxyhemoglobin levels with increasing clinical class in the standing position (P < .001). This finding was not observed in the supine measurements. ConclusionsIn CVD, HSI shows an increase in deoxyhemoglobin in the standing compared with supine position, particularly in the gaiter region. Furthermore, standing deoxyhemoglobin increases as the CEAP clinical class increases. Thus, this noninvasive tool may respond to venous physiology and may supplement the clinical class of the CEAP classification system.