中文摘要：

反流是左心室辅助装置（LVAD）在运行过程中转速过低时出现的一种异常工况,会导致LVAD无法辅助自然心脏泵血,影响患者健康。根据反流程度的不同,本文定义了三种LVAD反流状态：无反流、轻度反流和重度反流,并基于动态封闭容腔理论,提出反流系数（RI）对其进行分级。数值结果表明,患者处于运动、静息和睡眠状态时,无反流和轻度反流的临界转速分别为6 650 r/min（运动）、7 000 r/min（静息）和7 250 r/min（睡眠状态）,对应RI值为0.401、0.300和0.238;轻度和重度反流的临界转速分别为5 500 r/min（运动）、6 000 r/min（静息）和6 450 r/min（睡眠状态）,对应RI值为0.488、0.359和0.284。此外,RI与转速呈负相关,确定相应的临界转速即可实现LVAD反流的分级。因此本文研究结果显示,基于流量信号的检测参数RI能有效地区分LVAD的反流状态,便于LVAD的反流检测,为LVAD的高可靠性控制系统的制定提供理论依据和技术支持。

英文摘要：

Regurgitation is an abnormal condition happens when left ventricular assist devices （LVADs） operated at a low speed, which causes LVAD to fail to assist natural blood-pumping by heart and thus affects patients＇ health. According to the degree of regurgitation, three LVAD＇s regurgitation states were identified in this paper： no regurgitation, slight regurgitation and severe regurgitation. Regurgitation index （R/）, which is presented based on the theory of dynamic closed cavity, is used to grade the regurgitation of LVAD. Numerical results showed that when patients are in exercising, resting and sleeping state, the critical speed between slight regurgitation and no regurgitation are 6 650 r/rain, 7 000 r/min and 7 250 r/min, respectively, with corresponding RI of 0.401, 0.300 and 0.238, respectively. And the critical speed between slight regurgitation and severe regurgitation are 5 500 r/min, 6 000 r/min and 6 450 r/rain, with corresponding RI of 0.488, 0.359 and 0.284 respectively. In addition, there is a negative relation correction between RI and rotational speed, so that grading the LVAD＇s regurgitation can be achieved by determining the corresponding critical speed. Therefore, the detective parameter RI based on the signal of flow is proved to be able to grade LVAD＇s regurgitation states effectively and contribute to the detection of LVAD＇s regurgitation, which provides theoretical basis and technology support for developing a LVADs controlling system with high reliability.