Comparison and analysis of the Lyapunov exponents of blood flow signal of healthy and stenotic artery

The Lyapunov exponent is an important index reflecting dynamic characteristics of nonlinear systems. In order to study the value of the largest Lyapunov exponent on diagnosing the arterial stenosis in various degrees, we acquired the blood flow signal on the healthy and stenotic internal carotid arterial in white rabbits by transcranial Doppler ultrasound and the collection system of Doppler ultrasound's signal designed by ourselves, calculated the largest Lyapunov exponents respectively, analyzed and compared the dynamic state of the blood flow. The results show that the largest Lyapunov exponents of the blood flow signal in the white rabbits with the healthy internal carotid arterial are negative, and the blood flow is non-chaos. The largest Lyapunov exponents of the blood flow signal in the white rabbits with the stenotic internal carotid arterial are positive, and the blood flow is chaos. The larger the value of the largest Lyapunov exponent is, the higher the degree of stenosis is. Perhaps, it will provide a new approach to diagnose the arterial stenosis.