Laser Doppler Vibrometry for Assessment of Pulse Wave Velocity Application in an Experimental Setup and in Living Subjects

When a fluid flowing through an elastic vessel is subjected to a sudden change in pressure gradient, pressure pulses will propagate through the fluid. Velocity of these pulse waves (PWV) can be determined by simultaneous detection of wall distension on two separate points on the vessel wall, along its trajectory. PWV depends on wall stiffness, and under certain circumstances, wall stiffness can be calculated from the propagation velocity. In vivo detection of arterial PWV can have applications in cardiovascular risk management. Stiffness of large arteries has a very good predictive value for cardiovascular disease and overall mortality. This parameter can be estimated from arterial PWV. Current methods to measure arterial PWV suffer from several shortcomings. Laser Doppler vibrometry (LDV) can offer substantial advantages over existing techniques. In this work, we propose LDV as a noncontacting technique that allows measurement of wall distension on discrete locations. With two commercial vibrometers, we measured PWV in silicon tubes with different wall properties. Consequently, we determined PWV in living subjects. In a first step towards miniaturization, we used a custom built dual-beam LDV, with one laser source and one acousto-optic modulator (AOM) to evaluate PWV in elastic vessels. While measurements of PWV in living subjects with the dual-beam LDV are ongoing, we found that PWV as measured in elastic vessels agrees well with theoretically expected values, and measurement precision is better than 5%. Results of arterial PWV corresponded well with literature, but could not yet be validated. 10th IMEKO TC14 Symposium on Laser Metrology for Precision Measurement and Inspection in Industry Braunschweig, GERMANY, 2011, September 12-14