Development and Implementation of Control Strategy for Artificial Hearts from the Aspect of Complex Systems and Artificial Life

点击翻译按钮获取中文摘要

Strictly speaking, the cardiovascular system is a complex system with large-scale, multivariate, nonlinear and nonstationary characteristics. The purpose of this study was to develop control strategies for artificial hearts in consideration of the characteristics of the cardiovascular system regarded as a living system. The fruits yielded by this study are shown below.First, we proposed a nonlinear model to simulate time trajectories of stroke volume and blood pressure by introducing a feedback effect reflecting autonomic nervous information based on heart rate variability. This model can generate a chaotic heart rate variability whose characteristic differs between rest and exercise conditions. The model seems to be adequate because responses of heart rate variability similar to the above one were found in a healthy human subject.Secondly, we discussed whether the cardiac function of the natural heart can be estimated even in a complex system such as a circulatory system assisted by a … More ventricular assist device (VAD) using continuous-flow pump in which the VAD and the natural heart are competing against each other. The results obtained from animal experiments showed that an index Emax could be estimated to some extent in such a complex situation. It was also suggested that a dynamic model based on differential equation should be considered for analysis rather than a static model even if a continuous-flow VAD is used because beating components caused by the natural heart cannot be ignored.Thirdly, we proposed a new method for estimating outflow of a continuous-flow VAD using an ARX model. It was ascertained that the accuracy of the proposed method remained on a practical level for two weeks in an animal experiment.Finally, we developed a transcutaneous energy and signal transmission system by using a new special type of coil with a good decoupled characteristic between energy and information. An in vitro experiment indicated that the system is useful for applying to clinical situations because of its robustness against positional deviation. Less