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

最大心室弹性（Emax）是一个很好的定量指标，如果Emax可以低创地获得，将是脱离心室辅助装置的一个很好的指标。本研究的目的是开发一种估算Emax搏动和低侵入性的方法。首先，将Emax的估计过程表述为一种逆问题。这就产生了一种算法，该算法仅基于两个测量值来估计Emax的搏动：心室压和心室容积或主动脉流量。其次，在个人计算机系统上实现了算法，实现了Emax的实时计算。第三，山羊动物实验在改变前负荷和后负荷或注射改变心功能的多种情况下进行。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监测心功能是足够有用的。此外，由于该方法的估计误差可以定量地评价为相对于收缩期末压力体积回归线截距的误差，因此该方法优于传统方法。为了将所提出的方法应用到实际的临床环境中，必须进一步改进所提出的方法，以便使用其他侵入性较小的信息，如主动脉压，而不是心室压来估计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.