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

如果最大心室弹性(Emax)能够以低创的方式获得，那么Emax将是一个很好的量化指标，可以帮助患者脱机。本研究的目的是开发一种估计Emax的方法，首先，Emax的估计过程是一种反问题。其次，该算法在个人计算机系统上实现，以实时计算Emax；第三，在山羊身上进行动物实验，在许多情况下，改变前负荷和后负荷或注射改变心功能。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，由于估计误差可以作为相对于收缩末压-容量回归线截距的误差来定量评估，因此该方法优于传统方法。要将该方法应用于实际临床环境，该方法还需要进一步改进，以便可以使用另一种侵入性更小的信息，如主动脉压而不是室压来估计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.