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

严格地说，心血管系统是一个具有大规模、多变量、非线性和非平稳特性的复杂系统。本研究的目的是开发人工心脏的控制策略，考虑到心血管系统作为一个生命系统的特点。本研究取得的成果如下：首先，通过引入基于心率变异性的反映自主神经信息的反馈效应，提出了模拟心搏量和血压时间轨迹的非线性模型。该模型可以产生一个混沌的心率变异性，其特征在休息和运动条件下不同。该模型似乎是适当的，因为在健康人受试者中发现了类似于上述心率变异性的响应。其次，我们讨论了即使在复杂的系统中，例如在循环系统辅助下，天然心脏的心脏功能是否可以估计。 ...更多信息 心室辅助装置（VAD）使用连续流泵，其中VAD和自然心脏相互竞争。动物实验结果表明，在这种复杂的情况下，Emax指数可以在一定程度上进行估计。同时，由于心脏的搏动成分不可忽略，因此，即使使用连续流VAD，也应该考虑基于微分方程的动态模型进行分析，而不是静态模型。第三，提出了一种基于ARX模型的连续流VAD流出量估计方法。在动物实验中，可以确定所提出的方法的准确度在两周内保持在实用水平。最后，我们利用一种新型特殊类型的线圈，在能量和信息之间具有良好的解耦特性，研制了一种经皮能量和信号传输系统。体外实验表明，该系统是适用于临床情况，因为它的鲁棒性对位置偏差。少

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