Valores de referência para níveis de perfusão tecidual e uso da near-infrared spectroscopy (NIRS) em indivíduos com diabetes

Abstract

Near-Infrared Spectroscopy (NIRS) is a non-invasive method for continuous monitoring of tissue oxygenation and hemodynamics, brain and muscle, which has recently been used to investigate local muscle oxidative metabolism at rest and during exercise, both in athletic performance and in clinical situations involving health conditions. One of the main factors responsible for morbidity and mortality in individuals with type 2 diabetes mellitus (T2DM) is peripheral arterial disease (PAD). In this sense, especially in individuals with T2DM who have vascular repercussions and are often asymptomatic, NIRS would enable a broader understanding of muscle metabolism. However, there are no records in the literature of reference values of tissue oxygen saturation (StO2) of the main musculature affected by PAD, the sural triceps, which would allow a deeper understanding of the results provided with NIRS in DM2 without apparent PAD. Therefore, the aim of this thesis was to determine reference values for lower limb peripheral tissue perfusion assessed by NIRS and to explore the applicability of NIRS use in individuals with T2DM. Therefore, two studies were developed, the first aimed to determine reference values for peripheral tissue perfusion of the lower limb assessed by NIRS, at rest and in progressive effort, in apparently healthy individuals. In a Minas Gerais municipality, between August 2018 and July 2019, 288 apparently healthy individuals between 30 and 79 years of age were selected. The selected individuals underwent anthropometric, physical activity level, and StO2 assessments during and after the arterial occlusion maneuver and the incremental shuttle walking test (ISWT) using the NIRS. In this study, it was observed that the median (P50) of StO2 basal (StO2-basal) and of lowest StO2 obtained (StO2-lowest) are lower in men than in women, being at rest the StO2-basal 6% lower and the StO2-lowest 17% lower. In effort this difference reduces to 3% and 10%, respectively, and in addition, a lower median value of StO2-final and a longer time to reach StO2-lowest is observed for men. Unlike the StO2 values, the median deoxygenation (Tx-desox) and reoxygenation (Tx-reox) rates are higher in men at rest, as well as the Tx-reox in effort. According to the results presented in percentile values, in a apparently healthy sample from 30 to 79 years of age, there is gender difference in the distribution of peripheral lower limb StO2, which remains in the different age groups with a reduction tendency of StO2 with advancing age. In the second study the objective was to compare parameters of peripheral tissue perfusion of the lower limb at rest, during and after progressive effort between individuals with T2DM without apparent vascular disease and apparently healthy individuals, and to evaluate the factors associated with peripheral tissue perfusion of the lower limb in individuals with T2DM during progressive effort. Participated in this stage 62 subjects, 31 with DM2 and 31 apparently healthy. In the group with T2DM, the brachial ankle index, waist-hip ratio, waist circumference and biochemical test results were evaluated. And in both healthy and T2DM groups, body fat percentage (BFP), body mass index, physical activity level were evaluated; and also through NIRS, peripheral tissue perfusion values were evaluated during and after the arterial occlusion maneuver and the ISWT. The main findings of this study were the significantly lower value of StO2-lowest during exercise in the DM2 group compared to the healthy group (p=0.005), and from this result, a significant association was found between this variable and the level of physical activity (p<0.001; r= -0.681), total (p=0.001; r=0.590) and segmental (p<0.001; r=0.625) BFP. Thus, with article 1, reference values were adequately defined for lower limb tissue perfusion; and article 2 indicated some early alteration of lower limb tissue perfusion in the DM2 group, which has not yet clinical repercussions, and simple routine measures were indicated that may help to understand tissue microcirculation in individuals with T2DM without apparent vascular alteration, thus allowing clinical management to precede vascular complications.