Assessing Leg Blood Flow In Multiple Locations Using Multiple Near-infrared Spectroscopy Devices

Purpose: Leg blood flow has been measured using a single near-infrared spectroscopy (NIRS) device after exercise or ischemia. This study evaluated leg blood flow using three NIRS devices on three locations, using cuff ischemia and postural ischemia. The aim was to determine the optimal method and duration for these measurements. Methods: Young, healthy adults (males: n = 5 and females: n = 2) were tested on two separate days. Blood flow was measured as the half-time of recovery (T1/2) of the NIRS tissue saturation index (TSI) after leg lifts (60s, 120 s) or cuff ischemia (30s, 60s, 180 s, 300 s). NIRS devices were placed on the vastus lateralis, medial gastrocnemius, and Extensor digitorum brevis. T-tests were made to compare values between days and tests. Results: All subjects preferred the leg lifts to cuff ischemia to measure blood flow. T1/2 values for 60 seconds and 120 seconds of leg lifts were 4.6 + 0 and 4.3 + 0 for the thigh, 5.9 + 2.5 and 7.8 + 5.4 for the calf, and 6.1 + 2.6 and 8.4 + 4.1 for the foot. The values were 4.6 + 1.7, 7.0 + 3.7, and 9.6 + 6.0 for 30 seconds of ischemia. The values were 5.2 + 1.4, 7.6 + 6.3, and 9.0 + 6.2 for 60 seconds of ischemia. The values were 7.2 + 1.3, 12.0 + 5.4, and 13.8 + 5.5 for 180 seconds of ischemia. The values were 9.2 + 1.8, 15.1 + 6.2, and 16.7 + 5.4 for 300 seconds of ischemia. The mean values were not different between leg lift durations and were slower in the foot in comparison to the thigh values for all measures. There was a significant difference between thigh and foot measurements for most durations. Conclusions: Leg lifts are a subject's preferred method to measure blood flow in the leg. Normal values for the foot will be longer than for the calf and the thigh.