Micro-vascular Blood Flow During Post-Occlusive Reactive Hyperemia Assessed By Diffuse Correlation Spectroscopy

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PURPOSE: The purpose of this investigation was to determine if Diffuse Correlation Spectroscopy (DCS) provides a reproducible measure of micro-vascular blood flux during post-occlusive reactive hyperemia (PORH). Previous techniques utilized to assess forearm muscle blood flow include brachial artery blood flow and Near Infrared Spectroscopy (NIRS). DCS provides a novel ability to examine red blood cell (RBC) flux within the muscle microvasculature. We hypothesized that DCS would provide a reproducible measure of muscle microvasculature RBC flux during PORH. METHODS: 7 healthy male subjects (25.9 ± 4 yrs) performed 3 trials of brachial artery PORH tests. The DCS probe was placed on the flexor digitorum superficialis m. of the cuffed arm and provided Blood Flow Index (BFI). Brachial artery blood flow was assessed using Doppler Ultrasound to provide time-averaged maximum velocity (TAMAX). Following a 10 min supine rest period baseline measurements were performed for 1 min at which time a pneumatic cuff was inflated to at least 250 mmHg for 5 minutes. Measurements continued to be made for the 5 min of occlusion and 3 min post cuff release. The subjects were given 10 min rest between trials. RESULTS: The peak TAMAX of the brachial artery for PORH1, PORH2, and PORH3 occurred at 7.3 ± 3.4, 6.0 ± 2.4, and 6.4 ± 2.7 sec respectively (p=0.397). The peak in BFI for PORH1, PORH2, and PORH3 occurred at 25.6 ± 4.5, 26.4 ± 8.3, and 22.3 ± 3.5 sec respectively (p=0.311). The time to peak for TAMAX was significantly different from the time to peak in BFI (p<0.001). CONCLUSIONS: Similar time to peak for BFI across trials indicates that the DCS provides a reproducible signal of muscle microvasculature blood flux during PORH conditions. We speculate that the significant difference between time to peak for TAMAX and BFI may be due to compliance between the brachial artery and the microvasculature.