Characteristics of laser Doppler flowmeters with differing optical arrangements

Recently, various laser Doppler flowmeter (LDF) systems have been used for evaluation of tissue microcirculation. However, indifference has often been shown by doctors and researchers regarding their sampling volume, stability and accuracy, which differ with various optical arrangements. In this study we evaluated the characteristics of three LDF systems with different optical arrangements. The sampling depths in both blood and tissue were found to differ with the different optical arrangements, although the laser power emitted from the probes is nearly equivalent. Each depth significantly changed at haematocrits between 5.0 and 36.5%. The stability and the accuracy of the measurements also differed. In the practical case of tissue microcirculation it is important to measure blood flow with an understanding of the material differences in the characteristics of the LDF systems.