Assessment of human muscle blood perfusion with single-fiber laser Doppler flowmetry

Laser Doppler flowmetry (LDF) is a technique for continuous monitoring of microvascular perfusion. Commercially available flowmeters in general are equipped with probes constructed for performing measurements on superficial tissue surfaces, but small (phi = 0.45 mm) metallic needle probes for in-tissue measurements are also available. In this study a flexible single-fiber LDF probe with a total diameter of 0.5 mm has been inserted into human tibial muscle and used for assessment of local muscle blood flow. Local muscle perfusion shows a considerable spatial variation. If the probe position is not changed between consecutive measurements, reproducible curve parameters are obtained. Vasomotion was not observed in any measurement. The hyperemic blood flow response was recorded after tourniquet deflation. Time to reach peak magnitude as well as duration of the hyperemic blood flow response was increased significantly (P less than 0.01) with prolonged occlusion time. The response was found in both skin and muscle blood flow recordings. Increasing occlusion time from 3 to 5 min did not significantly enhance the results. Comparison of skin and muscle responses with respect to time to reach peak magnitude showed a significant difference (P less than 0.02) for the 1-min occlusion. A significant increase (P less than 0.01 and 0.05 for muscle and skin, respectively) in peak flux was seen in muscle and skin when tourniquet occlusion was increased from 1 to 3 min. Further increases in occlusion time did not produce significant increases in peak flux. The technique is easy to use, and may be of value in studies of disturbances of perfusion in muscle and possibly in parenchymatous organs (transplantation surgery) and central nervous system circulation.