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

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 (StO(2)) 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 StO(2) 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 StO(2) 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 StO(2). The % FMD was significantly correlated with the reperfusion slope of StO(2) after cuff release (slope 2 StO(2); r = 0.63, P = 0.003). In conclusion, the present study established a correlation between slope 2 StO(2) and % FMD in healthy youngmen. These data suggest that NIRS-derived slope 2 StO(2) can be used as a measure of vascular endothelial function.