Evaluation of an infrared laser-Doppler blood flowmeter

Abstract

Several laser-Doppler blood flowmeters are now commercially available; however, only one utilizes an infrared laser diode (Laserflo, TSI, St. Paul, MN). Because of this and other unique features such as its microprocessor-based signal analyzer, we evaluated this device's ability to measure tissue perfusion. Initially, we determined whether laser illumination directly affected the microvasculature. Intravital microscopic observations in the hamster cremaster muscle indicated that neither He-Ne nor infrared laser light affected the diameters of arterioles that were responsive to vasoactive agents. To test the flowmeter for linearity and repeatability, we used a rotating disk to simulate a light-scattering, flowing medium. The "flow" signal was highly correlated (r = 0.99) with the rotational velocity of the disk, was consistent among flow probes, and showed a high degree of reproducibility. The second model consisted of microsphere suspensions pumped through cuvettes. The laser-Doppler velocimeter (LDV) flow signal was linear with respect to pump output. With red blood cells in the perfusate, we examined the effects of blood oxygenation on the flowmeter's performance. The LDV flow signal was unaffected by changes in blood oxygenation. We evaluated linearity in vivo in isolated, perfused rat livers and in isolated canine gastric flaps. We observed linear relationships between total flow and laser-Doppler flow measured on the surface of the liver (r = 0.98) and in the gastric mucosa (r = 0.98), but the slopes of the relationships between total and local LDV flow showed considerable variability not noted in the in vitro studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of methodological developments in laser Doppler flowmetry

“…Obeid [65] used a similar flow model to check the linearity of the velocity response of different signal processing algorithms. Another approach was the use of solid-based systems in which a layer was rotated or translated between a sandwich of stationary layers [67]. De Mul et al [68], and Steenbergen and De Mul [69] reported on a standard consisting of a set of layers containing scattering and absorbing particles, either at rest or moving with respect to each other.…”

Nitric oxide production by tumour tissue: impact on the response to photodynamic therapy

“…Unanaesthetized mice were immobilized exposing their tumour-bearing leg; tumour size was as described for PDT treatment. Blood flow in superficial tumour regions was measured using a laser Doppler flowmeter (Laserflo Perfusion Monitor, Model BPM 403; TSI, Inc., St Paul, Minnesota, USA), which registers tissue microvascular flow continuously and noninvasively with a spatial resolution of approximately 1 mm 3 (Shepherd et al, 1987). The contribution of the superficial skin was found not to obscure tumour-related blood flow changes measured by this instrument (Durand and LePard, 1994).…”

Using multifractal detrended fluctuation analysis to assess sacral skin blood flow oscillations in people with spinal cord injury

“…Previous studies have shown that the LDF signal is independent of the effect of the absorption characteristics of the blood for a given LDF system as the fiber separation and wavelength are fixed [32][33][34]. Shepherd et al reported that laser Doppler velocity signals are unaffected by changes in blood oxygenation [32]. Nilsson et al evaluated skin blood flow measurements based on the laser Doppler principle and found a linear relationship between flowmeter response and flux of red blood cells [33].…”