Development of Low-Invasive Estimation System of Maximum Ventricular Elastance Emax Under Assisted Circulation

最大心室弹性（Emax）如果能够在低创条件下获得，将是一个很好的定量指标，用于患者从心室辅助装置中撤机。本研究的目的是开发一种方法来估计Emax的逐搏和低侵入性。首先，它被制定为估计Emax的过程是一种逆问题。这导致了一种算法，用于估计Emax的基础上只有两个测量心跳：心室压力和心室容量或主动脉流量。第二，该算法是在个人计算机系统上实现的，以计算Emax的实时方式。第三，动物实验中使用山羊进行了许多情况下的变化，在前负荷和后负荷或注射改变心脏功能。实验数据表明，该方法与传统方法的Emax相关系数约为0.9。这表明所提出的方法对于监测心脏功能是足够有用的。此外，它可以表明，所提出的方法是上级优于传统的方法，因为估计误差可以定量地评估为相对于收缩末期压力容积回归线的截距的误差。建议的方法必须进一步改进，以便另一个较少-例如主动脉压力而不是心室压力的侵入性信息可以用于估计Emax。

The maximum ventricular elastance (Emax) will be a good quantitative index for weaning the patient from the ventricular assist device if the Emax can be obtained low-invasively. The purpose of this research was to develop a method for estimating the Emax beat-to-beat and less-invasively.First, it was formulated that the process for estimating the Emax is a kind of inverse problem. This leaded to an algorithm for estimating the Emax beat-to-beat on the basis of only two measurements : ventricular pressure and ventricular volume or aortic flow.Second, the algorithm was implemented on a personal computer system to calculate Emax in a real-time fashion.Third, the animal experiments using goats were carried out in many situations with change in preload and afterload or with injections for changing cardiac function. The data obtained from the experiments)showed that the correlation coefficient of the Emax between the proposed method and the traditional method was about 0.9. This indicates that the proposed method is sufficiently useful for monitoring cardiac function. Furthermore, it could be shown that the proposed method is superior to the traditional methods because the estimation error can be evaluated quantitatively as an error with respect to the intercept of the end-systolic pressure volume regression line.To apply the proposed method to actual clinical settings, the proposed method must be further improved so that another less-invasive information like aortic pressure instead of ventricular pressure can be used for estimating the Emax.