Abstract 337: Measurements of Calf Muscle Oxygenation During Standing and Exercise in Patients with Chronic Venous Insufficiency

Abstract

BACKGROUND Despite the established role of the calf muscle pump for preventing chronic venous insufficiency (CVI), hemoglobin flow in the calf muscle is poorly understood. Near-infrared spectroscopy (NIRS) provides continuous noninvasive monitoring of changes in tissue oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) levels. The purpose of this study was to investigate the changes in calf muscle HbO2 and HHb levels during standing and exercise in patients with CVI. METHODS Seventy-four limbs in 73 patients with various clinical stages of CVI were enrolled. Patients were divided into early (C0-C3) and advanced (C4a-C6) according to the CEAP classification. NIRS was used to measure changes in the calf muscle HbO2 and HHb levels, and oxygenation index (HbD; HbD=O2Hb-HHb) while lying spine, standing, and then subsequently performing 10 tiptoe movements. RESULTS Among the 74 limbs evaluated, 47 had early and 27 had advanced CVI. Standing caused increases in both O2Hb and HHb levels. However, there were no significant differences in these increases, or HbD, between early and advanced CVI. In contrast, the time elapsed until the maximum increase in O2Hb concentration was significantly reduced in patients with advanced CVI in comparison with patients showing early CVI (55.5 ± 44.2, 32.6 ± 12.6 s, P=.025). During 10 tiptoe movements, a decrease in O2Hb concentration was observed, and there was no significant difference in the reduction of O2Hb values between early and advanced CVI. In contrast, 10 tiptoe movements produced venous emptying (HHbE) and subsequent retention (HHbR), and the HHbR was significantly increased in patients with advanced CVI compared with those with early CVI (6.0 ± 7.0, 9.0 ± 6.2 μmol/L, P=0.021). Furthermore, HbD falls were more pronounced in patients with advanced CVI (7.4 ± 11.5, -5.9 ± 15.7 μmol/L, P=0.002). CONCLUSIONS Changes in O2Hb and HHb concentrations differ between early and advanced CVI during standing and exercise. Detailed investigation of the interrelationship between O2Hb and HHb during calf muscle pump function would lead to a better understanding of the various clinical stages of CVI.