Near infrared spectroscopy (NIRS) a non-invasive technique used to measure tissue perfusion and oxygenation. Recent studies used the combination of a Venous occlusion plethysmography (VOP) with NIRS to study microvascular function. NIRS have demonstrated to monitor effectively perfusion changes in muscle microcirculation. The purpose of this study was to determine If NIRS can predict microvascular blood flow measurement via VOP.
A total of 20 young apparent healthy subjects, were recruited for this study. NIRS and VOP were performed simultaneously at the right forearm and right calf. VOP strain gauges placed around the widest part of both extremities between cuffs. Probes for NIRS were placed on forearm and calf both perpendicular to the longitudinal axis. Baseline levels were obtained for a minute for NIRS and VOP. Followed by an ischemic stress were cuffs were inflated to a suprasystolic pressure for five minutes. Post ischemic stress data was collected for one minute. Strength association was evaluated by Pearson correlation.
Lower extremity demonstrated a positive correlation with average basal oxyhemoglobin (HbO₂) versus, slope of deoxyhemoglobin (HHb) (R= 0.541: P= 0.014). HHb 30 seconds before ischemic stress is release had a positive correlation with tissue oxygen saturation (SO2) slope (R =0.873; P <0.05). HHb post ischemic stress slope had a positive correlation with HbO₂ slope (R = 0.665; P =0.001). Upper extremity, HbO₂ post ischemic stress versus HHB post ischemic stress showed a positive correlation. (R = 0.916; P = <0.05). HbO₂ 30 seconds before ischemic stress versus HHB 30 seconds before ischemic stress slope had a positive correlation (R= .784; P = <.05). No correlation was found with VOP measurements.
There were no agreements between NIRS and VOP, for the assessment of microvascular function.