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SEGMENTAL LEG BLOOD FLOW MEASURED WITH NEAR-INFRARED SPECTROSCOPY

Abstract

Jalyn A. Boyles, Ryan J. Willoughby, Hieu T. Vu, Chloe E. Blum, Zabilon S. Dessalegn, Abisola R. Akinbobola, Kevin K. McCully, FACSM. University of Georgia, Athens, GA.

BACKGROUND: Peripheral arterial disease (PAD) is a significant cause of morbidity and mortality worldwide. The ankle brachial systolic blood pressure is typically used to evaluate patients with PAD; however, it is not sensitive to mild disease and confounded by hardening of the arteries. Alternatively, near-infrared spectroscopy (NIRS) can measure blood flow as the rate of recovery oxygen saturation after ischemia. This study determined the shortest ischemic duration with acceptable reproducibility for NIRS measuring blood flow in three locations concurrently. METHODS: We tested young, healthy, male (n=6), and female (n=1) subjects on two separate days. NIRS was simultaneously measured on the vastus lateralis, medial gastrocnemius, and foot pad of the right leg. The half time (T½) of oxygen saturation was measured after four ischemic cuff durations (30, 60, 180, 300 seconds). The cuff durations were randomized for testing but are presented in ascending order. Paired t-tests were used to compare day one to day two measures in four different locations. RESULTS: The T½ for the foot was 13.0 ± 7.3, 13.5 ± 6.5, 12.7 ± 3.7, 15.1 ± 4.4 seconds. The T½ for the calf was 8.5 ± 4.3, 5.0 ± 1.9, 6.2 ± 1.7, 8.8 ± 4.1 seconds. The T½ for the thigh was 6.6 ± 4.6, 6.0 ± 2.4, 6.2 ± 1.7, 8.5 ± 2.5 seconds. The tissue saturation index (TSI) percent values for the foot were 2.1 ± 0.9, 4.5 ± 2.1, 13.2 ± 11.6, 20.1 ± 16.7. The values of the calf were 2.1 ± 1.5, 7.4 ± 3.7, 22.1 ± 13.1, 34.2 ± 20.4. The values for the thigh were 3.13 ± 0.8, 6.0 ± 3.1, 18.9 ± 12.1, 26.1 ± 17.6. There was no significant difference between day one and day two at any location. The foot pad T½ values were significantly longer than the muscle locations. Signal magnitudes were significantly higher for the 180 and 300 second cuff durations. CONCLUSIONS: Our results suggest the cuff duration of 180 seconds provided the shortest ischemic duration that produced adequate reproducibility and signal intensity. NIRS has the potential to measure blood flow in different locations of the legs of patients with PAD.

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