Nonlinear Dynamics Of The Instantaneous Fetal Heart Rate Signal Analysis

It is the most universal way to speculate the state of fetal in the womb through examining the heart rate. But up to now, most methods of analyzing heart rate are still through observing sensibly and statistical analyzing. These methods are too rough to reflect dynamic essence .So far as our opinion, most physiological signal are nonlinear, most probably so does heart rate of fetal. Therefore we think in the study of heart rate, it is important to know whether the heart rate of fetal has nonlinear character.In the following work, we will take fifteen group of heart rate of fetal as samples to make more comprehensive nonlinear analysis. After the study, we get the following results: its power spectrum is a continuous spectrum with pinnacles. This shows that the heart beat signal of fetal is not signal of noise, not periodic signal, but the signal, which may follow some dynamical laws. Under the condition of our getting embedding dimension and the delayed time ,we reconstruct the phase space and calculate the nonlinear parameters ,such as correlation dimensions ,the largest Lyapunov exponents , L-Z complexity, and approximate entropy .From the results ,we can conclude that the attractor of the heart beat rate signal is strange attractor, its correlation dimension is the fraction ,its largest Lyapunov exponent is positive,its approximate entropy and L-Z complexity are obviously differ from noise. All these indicate that the heart beat rate signal is not simple noise, not simple periodic signal; it is high dimensional chaotic signal, which obeys certain dynamical law. Last we analyze the data with RPA and get the same result.