Vascular responsiveness determined by near-infrared spectroscopy measures of oxygen saturation

Abstract

New Findings: What is the central question of this study? Can the near-infrared spectroscopy (NIRS)-derived reperfusion rate (slope 2) of tissue oxygen saturation (StO2) be correlated with flow-mediated dilation (FMD), the commonly used method to assess vascular endothelial function? What is the main finding and its importance? The present data were able to establish a correlation between the reperfusion rate of StO2 and percentage FMD in healthy young men. These data suggest that NIRS-derived slope 2 StO2 can be used as a measure of vascular endothelial function. Vascular impairments at the macro- and microcirculatory levels are associated with increased risk for cardiovascular disease. Flow-mediated dilation (FMD) is currently the most widely used method for non-invasive assessment of vascular endothelial function. Recently, near-infrared spectroscopy (NIRS)-derived measures of tissue oxygen saturation (StO2) have been used to characterize the dynamic response of local tissue perfusion to a brief period of ischaemia. The purpose of the present study was to establish correlations between the reperfusion rate of StO2 and FMD. Ultrasound-derived FMD was quantified after 5 min of distal cuff occlusion of the popliteal artery in 20 healthy young men (26 ± 3 years old). Triplicate measurements of end-diastolic arterial diameter were made every 15 s after cuff release, and FMD response was calculated as the greatest percentage change in diameter from baseline (%FMD). The StO2 was measured using NIRS throughout the duration of each test. Two consecutive FMD tests were performed, separated by 30 min of rest, and were averaged for %FMD and StO2. The %FMD was significantly correlated with the reperfusion slope of StO2 after cuff release (slope 2 StO2; r = 0.63, P = 0.003). In conclusion, the present study established a correlation between slope 2 StO2 and %FMD in healthy young men. These data suggest that NIRS-derived slope 2 StO2 can be used as a measure of vascular endothelial function.