The usefulness of a laser Doppler in the measurement of the blood pressures

Objective: The purpose of this study was to evaluate the clinical value and reproducibility of laser Doppler (LD) versus photoplethysmography (PPG) in the measurement of the systolic toe blood pressure. Methods: Toe blood pressure was measured in 60 patients in different stages of peripheral vascular disease with simultaneous digital sampling of PPG a nd two LD signals, each with a different filter setting (3 second [LD3] and 0.03 second [LD0.03]), and cuff pressure. These measurements were repeated after 1 week. The signals were analyzed with previous results ignored. The agreement of the PPG and LD pressures and reproducibility after 1 week wer e assessed by calculating the intraclass correlation coefficient (ICG). The agreement variation across the range of pressure values was visually explo red by means of difference plots. Results: In 19 legs with a very low pressure only LD could adequately measu re the pressure, whereas PPG did not. The ICCs between PPG and LD3 and LD0. 03 were 0.95 or more. The ICCs of the 1-week reproducibility of the PPG, LD 3, and LD0.03 pressures were 0.92, 0.88, and 0.86, respectively. The variat ion was equally distributed across the range of pressures in all three meth ods. Conclusion: LD is a reliable alternative to PPG to measure toe blood pressu res. Furthermore, LD is able to measure low pressures, which is relevant in the assessment of the presence of critical ischemia.