Effect of bifurcation on pulse wave propagation in human arteries

In recent years, arteriosclerotic cardiovascular disease becomes a serious problem in the developed countries. The degree of the arteriosclerosis should be examined routinely and invasively, and the measurement of pulse wave is considered as an effective estimation method. Nowadays, pulse wave is widely used in clinical practice as a noninvasive method of examining circulatory kinetics, but the mechanism in the process of the systolic wave generated at heart and propagating to the peripheral artery remains to be elucidated. In this research, to investigate the effect of bifurcation on pulse wave propagation, numerical simulations by a dynamic model of arteries and in vitro experiments were conducted. A onedimensional model of arteries is coupled by partial differential equations describing mass and momentum conservation with the tube law that relates the local cross-sectional area to the local radial pressure difference. In the case of a bifurcated artery model, the governing equations were solved by introducing the momentum caused by the reactive force at bifurcation into the equation of momentum conservation. The momentum by the reactive force at bifurcation was supposed to be proportional to the momentum flowing into the bifurcation, and the proportionality coefficient was derived from experiments. Then, the proposed one-dimensional model was validated by a comparison to experimental data. In the experimental setup, elastic tubes with different values of Young's modulus were tested to simulate human arteries. From the numerical and experimental results, it turns out that the characteristic waveforms of the pressure and velocity obtained from experiments are also captured by the numerical calculations.