Near-infrared spectroscopy assessment of microvasculature detects difference in lower limb vascular responsiveness in obese compared to lean individuals

Abstract

Background: Microvascular dysfunction is an early complication in obesity-related cardiovascular disease (CVD) that can lead to changes in hemodynamic function and endothelial cell expression throughout the vasculature that is vessel specific. This study aimed to evaluate whether the near-infrared spectroscopy (NIRS) combined with a vascular occlusion (VOT) assessment was capable of detecting differences in vascular responsiveness within the microvasculature of the lower limb between lean and obese individuals.

Methods and results: Twenty lean (BMI = 21.6 ± 1.3) and 17 obese individuals (BMI = 33.9 ± 1.1) participated in the study. Individuals underwent a VOT (5 min of baseline, 5 min of occlusion, and 8 min following cuff release) and vascular responsiveness was evaluated by the Slope 2 (Slope 2 StO₂) and the area under the curve (StO_2AUC) of oxygen saturation (StO₂) signal during reperfusion. The difference between the minimal and the maximal value of StO₂ was calculated as the Amplitude of the StO₂ response. The Slope 2 StO₂ of the obese individuals was smaller (0.68 ± 0.07%·s^-1) than the Slope 2 StO₂ of the lean individuals (1.08 ± 0.13%·s^-1;P < 0.05). The StO2_AUC of the obese was smaller (978 ± 169%·s^-1) than the StO2_AUC of the lean individuals (1708 ± 168%·s^-1; P < 0.001). The amplitude of StO₂ was smaller in obese individuals than the lean ones (30.4 ± 2.9 vs 21.6 ± 1.3 StO₂ (%), respectively; P < 0.05). There was a significant correlation between Slope 2 StO₂ and StO2_AUC for lean individuals (r = 0.745; P < 0.001).

Conclusion: This study demonstrated differences in vascular responses within the microvasculature of the lower limb between lean and obese individuals.

Keywords: Hyperglycemia; NIRS; Obesity; Vascular responsiveness.