基于两级级联神经网络估计血泵转速及压力变化对血流量的影响

背景：对人工心脏输出流量进行及时精确的检测直接关系到人工心脏在动物实验及临床应用中的效果,但实现起来却比较困难。 目的：探究辅助循环过程中,心血管血流动力学参数如何反映血泵的工作状态？通过体外辅助循环实验,结合理论分析法,以得到掌握血泵流量特性的神经网络结果。 方法：为了正确地评估和检测心室辅助装置中血泵的工作状态,建立两种不同类型的神经网络级联模型,评估血泵转速、压力的连续变化对流量的影响。在第一级中,运用BP神经网络来评估在血泵不同转速下连续变化的压力对流量的影响;在第二级中,运用径向基网络估计血泵转速连续变化对流量的影响。 结果与结论：将经训练的级联网络应用于评估转速、压力对流量造成的影响,其结果与以往的方法相比显示了很好的评估能力。     

应用驱动电机参数估测叶轮式血泵输出流量的无创性测量方法

临床应用中、对人工心脏的输出流量进行及时,精确的检测十分必要,但实现起来却比较困难,作者针对江苏大学生物医学工程研究所研制的叶轮式人工心脏,提出采用驱动电机参数（功率和转速）间接测量血泵输出流量的方法,从而避免引入传感器探针,降低测量装置的复杂性,减小感染机会,实验结果表明,这种测量方法法能够达到一定精度（误差＜5％）,具有进一步研究价值。     

叶轮设计对叶轮式人工心脏溶血性能的影响

为了评价人工心脏的叶轮设计对血泵溶血性能的影响 ,笔者设计加工了叶片角和叶片数分别为(2 0° ,6 )、(30° ,6 )、(40° ,6 )、(30°,5 )和 (30°,7)的五个对数螺线等角叶轮 ,并基于不同扬程和流量下的体外溶血试验 ,探讨了叶轮设计参数与血泵溶血性能之间的相关性 ,从而系统地评价血泵各设计及运行参数对溶血破坏的影响 ,获取了血泵最佳设计参数及运行工况点等重要数据。实验结果表明 :血泵采用叶片角为 30°的六叶叶片 ,进出口压力差 10 0mmHg ,流量 4L/min时 ,其对血细胞破坏最小。     

“费城”人工心脏系统的研制

一种新型的气动人工心脏系统已经在美国费城研制成功。这种人工心脏可减少血细胞损伤和血液凝固,并可实现大批量生产。系统产生的流量和,力波形接近于自然心脏产生的主动脉内流量和压力波形。人工心脏的血泵完全是用聚氨酯材料制成。血泵壳体用Pellethane 363-80AE热塑性聚氯酯板料由真空成型工艺制成。由泵壳内表面和血膜形成的血室内表面是用以上材料的溶液由浇涂工艺制成的。所以其内表面光滑无缝。另外,底盖接口     

基于电机参数的叶轮式人工心脏输出流量的无创性测量

临床应用中,对人工心脏的输出流量进行及时,精确的检测十分必要,但实现起来却比较困难,针对江苏理工大学生物医学工程研究所研制的叶轮式人工心,是出采用驱动电机参数（功率和转速）间接测量血泵输出流量的方法,从而避免引入传感器的探针,降低测量装置的复杂性,减小感染机会,实验结果表明：这种测量方法方法能够达到一定精神,具有进一步研究价值。     

叶轮泵式全人工心脏的结构设计及流体力学特性

目的通过模型样机研制和流体力学特性测试．探索以叶轮式血泵为结构基础的新型可完全植入的全人工心脏。方法全人工心脏模型样机分为左心泵和右心泵2个基本单位。2血泵均采用叶轮泵．共同设置在球形外壳中。2半球形外壳由高分子材料经激光快速成型制成．球形腔内设置固定左右心泵后对合为球形外壳．表面由医用聚氨酯橡胶涂层，直径55mm，总质量150g左右。在体外模拟循环台上对左心泵和右心泵的流体力学特性进行测试．主要观测指标为泵的转速、输出压力、流量、能耗和效率。模拟循环装置由模拟左右心房、血泵、阻力调节器、流量计串联组成，采用30％甘油水溶液作为循环介质。通过调节阻力测定特定泵转速下压力和流量。结果体外模拟测试表明全人工心脏模型样机可满足血液动力学基本要求，左心泵在9000-13000r／min转速条件下可以达到5-7L／min流量和13．3kPa（100mmHg）的压力输出，右心泵在约1／2左心泵转速和4．00kPa（30mmHg）后负荷下达到相似流量．可分别满足体、肺循环的要求。在该工作负荷条件下，2血泵的总效率约为14％。结论轴流泵作为人工心脏的血泵单位．流体力学特性可达到全人工心脏的基本要求．     

左心室辅助血泵体外血液动力学参数的测定

尽管在美国全植入式人工心脏已用于临床,但是还有许多问题尚待解决,因此利用左心室辅助血泵抢救心脏病处于危险状态的病人,仍是目前最有希望的一种方法。为此,天津市人工心脏协作组,参考有关国外资料,研制出三种类型的左心室辅助血泵(囊型、管型及涡型),并在研制的“体循环模拟台”上做了血液动力学参数的测定。主要测试了三种血泵的驱动压(正压与负压)、驱动频率(心率)、充盈压(回心压)对心排量、动脉压、静脉压的影响,并记录了上述各测定指标相应的动脉压力波形。并由测定结果算出每种血泵的—Q曲线(平均动脉压与心排量之间的关系)、每种血泵在不同驱动压下的每搏搏出量及其各种血泵的效率。从总的测定结果可以认为这三种血泵均能满足左心辅助心排量的需要,一般可达1—5升/分钟;另外,也找出了各种血泵最宜适的工作条件(指驱动压、驱动频率等);同时还比较了各种血泵彼此的优缺点,为改进血泵的设计制造提供了一些实验依据。     

安装气动式人工心脏后的血压和血泵输出量的长期监护

对于植入式人工心脏或心室辅助泵,除了需了解其泵率、充盈时间、射血时间外,泵的每搏输出量、心房压和动脉压以及泵内压也是重要的监护和控制参数。本文主要综述了气动式血泵植入后,对心房压、动脉压和泵输出量等作长期的间接检测方法,包括检测压力参数的气道压力法、气道压力与隔膜位置相结合法、充气囊泡测压法;检测泵输出量的隔膜运动测量法和多因素综合算法。     

心脏辅助与替代装置中的血泵

背景：心脏替代型血泵得到迅速地发展,不仅在结构上具有便携辅助式或体内植入式,性能上也通过了几代的改进而具有良好的生理相容性。 目的：介绍心脏可视化手术中人工心肺机用血泵,心脏终末治疗时机械替代用的各种辅助血泵和全人工心脏,并展望人工心脏未来发展的趋势。 方法：应用计算机检索维普数据库、IEEE Xplore数据库、Springer Link数据库及谷歌学术进行检索并参考相关书籍,以“血泵”、“人工心脏”为关键词,选择内容相关的文献。 结果与结论：共纳入43篇文献。血泵为实现心脏直视手术及心脏的终末治疗提供了可能性,有非常高的临床价值。但血泵从结构设计和控制方面都有待提高,其中做到血泵用材料与人体具有良好的生理相容性及生理参数的控制系统是目前血泵发展的关键问题。     

人工心脏泵辅助对左心室血流动力学影响的数值研究

目的采用数值模拟方法研究人工心脏辅助装置植入对左心室内血流动力学的影响。方法首先利用心血管集中参数模型获取了健康状态、心衰状态以及人工心脏泵辅助状态下收缩末期左心室三维几何模型,其中选取超弹性材料Ogden为心肌材料,以左心房压力,主动脉压力以及通过左心室容积计算获取的左心室壁面位移作为边界条件,利用CFD方法对上述三种情况进行左心室的数值模拟。同时对比了健康时的模拟结果和生理状态下的左心室压力,以及心衰和人工心脏泵辅助两种状态下的血流动力学指标的差别。通过左心室压力和流速等评价灌注和负荷的情况,通过壁面切应力和涡流,评价人工心脏泵辅助后的左心室血流动力学变化规律。结果健康状态下模拟的左心室压力与生理指标相符合。在心衰和人工心脏泵辅助状态下,收缩期内左心室压力与健康状态比分别降低了1718 Pa和8455 Pa,辅助后左心室最大压力下降速度高于心衰时。人工心脏泵辅助后,舒张期壁面切应力峰值由4.3 Pa降低至3.8 Pa,收缩期壁面切应力峰值由4.1 Pa降低至1.3 Pa,射血速度峰值由1.61 m/s降低至0.68 m/s,主动脉瓣开放时间由0.25 s增加至0.65 s,左室射血分数由43.6%增加至52.7%,心室底端漩涡持续时间由0.35 s增加至0.51 s,顶端漩涡出现血流分离。结论左心室压力对比表明本研究方法可以用来模拟左心室的行为。人工心脏泵辅助能够快速降低心室内压力和心室负荷,增加灌注时间,提高器官灌注,降低左心室壁面切应力以及提高左心室内血液流场的涡流强度,延长涡流持续时间。     

Electric analogue model of the singleneedle extracorporal blood-circulatory system of an artificial kidney

Using an electric analogue model, the flow conditions (the progress over time of blood pressure and blood flow) within the single-needle extracorporal bloodcirculatory system of an artificial kidney are investigated. Two different arrangements are taken into consideration: a system with a nonpulsatile pump (a roller pump) and a system with a pulsatile pump (two roller pumps, or one bellows pump). It is demonstrated that, using a pulsatile pump and an optimised pump frequency, it is possible to achieve a reduction in pressure variations as well as flow-velocity variations (with a correspondingly reduced haemolysis rate), and also to achieve an increase in the mean blood flow (comparable to a two-needle system).     

Measurement of rotary pump flow and pressure by computation of driving motor power and speed

Measurement of pump flow and pressure by ventricular assist is an important process, but difficult to achieve. On one hand, the pump flow and pressure are indicators of pump performance and the physiologic status of the receptor, meanwhile providing a control basis of the blood pump itself. On the other hand, the direct measurement forces the receptor to connect with a flow meter and a manometer, and the sensors of these meters may cause haematological problems and increase the danger of infection. A novel method for measuring flow rate and pressure of rotary pump has been developed recently. First the pump performs at several rotating speeds, and at each speed the flow rate, pump head and the motor power (voltage x current) are recorded and shown in diagrams, thus obtaining P (motor power)-Q (pump volume) curves as well as P-H (pump head) curves. Secondly, the P, n (rotating speed) values are loaded into the input layer of a 3-layer BP (back propagation) neural network and the Q and H values into the output layer, to convert P-Q and P-H relations into Q = f (P,n) and H = g (P, n) functions. Thirdly, these functions are stored by computer to establish a database as an archive of this pump. Finally, the pump flow and pressure can be computed from motor power and speed during animal experiments or clinical trials. This new method was used in the authors' impeller pump. The results demonstrated that the error for pump head was less than 2% and that for pump flow was under 5%, so its accuracy is better than that of non-invasive measuring methods.     

Measurement of rotary pump flow and pressure by computation of driving motor power and speed

Measurement of pump flow and pressure by ventricular assist is an important process, but difficult to achieve. On one hand, the pump flow and pressure are indicators of pump performance and the physiologic status of the receptor, meanwhile providing a control basis of the blood pump itself. On the other hand, the direct measurement forces the receptor to connect with a flow meter and a manometer, and the sensors of these meters may cause haematological problems and increase the danger of infection. A novel method for measuring flow rate and pressure of rotary pump has been developed recently. First the pump performs at several rotating speeds, and at each speed the flow rate, pump head and the motor power (voltage x current) are recorded and shown in diagrams, thus obtaining P (motor power) - Q (pump volume) curves as well as P - H (pump head) curves. Secondly, the P, n (rotating speed) values are loaded into the input layer of a 3-layer BP (back propagation) neural network and the Q and H values into the output layer, to convert P-Q and P-H relations into Q=f (P,n) and H=g (P, n) functions. Thirdly, these functions are stored by computer to establish a database as an archive of this pump. Finally, the pump flow and pressure can be computed from motor power and speed during animal experiments or clinical trials. This new method was used in the authors' impeller pump. The results demonstrated that the error for pump head was less than 2% and that for pump flow was under 5%, so its accuracy is better than that of non-invasive measuring methods.     

Indirect flow rate estimation of the NEDO PI Gyro pump for chronic BVAD experiments

In totally implantable ventricular assist device systems, measuring flow rate of the pump is necessary to ensure proper operation of the pump in response to the recipient's condition or pump malfunction. To avoid problems associated with the use of flow probes, several methods for estimating flow rate of a rotary blood pump used as a ventricular assist device have been studied. In the present study, we have performed a chronic animal experiment with two NEDO PI gyro pumps as the biventricular assist device for 63 days to evaluate our estimation method by comparing the estimated flow rate with the measured one every 2 days. Up to 15 days after identification of the parameters, our estimations were accurate. Errors increased during postoperation days 20 to 30. Meanwhile, their correlation coefficient r was higher than 0.9 in all the acquired data, and estimated flow rate could simulate the profile of the measured one.     

Viscosity-adjusted estimation of pressure head and pump flow with quasi-pulsatile modulation of rotary blood pump for a total artificial heart

Estimation of pressure and flow has been an important subject for developing implantable artificial hearts. To realize real-time viscosity-adjusted estimation of pressure head and pump flow for a total artificial heart, we propose the table estimation method with quasi-pulsatile modulation of rotary blood pump in which systolic high flow and diastolic low flow phased are generated. The table estimation method utilizes three kinds of tables: viscosity, pressure and flow tables. Viscosity is estimated from the characteristic that differential value in motor speed between systolic and diastolic phases varies depending on viscosity. Potential of this estimation method was investigated using mock circulation system. Glycerin solution diluted with salty water was used to adjust viscosity of fluid. In verification of this method using continuous flow data, fairly good estimation could be possible when differential pulse width modulation (PWM) value of the motor between systolic and diastolic phases was high. In estimation under quasi-pulsatile condition, inertia correction was provided and fairly good estimation was possible when the differential PWM value was high, which was not different from the verification results using continuous flow data. In the experiment of real-time estimation applying moving average method to the estimated viscosity, fair estimation could be possible when the differential PWM value was high, showing that real-time viscosity-adjusted estimation of pressure head and pump flow would be possible with this novel estimation method when the differential PWM value would be set high.     

Modeling and identification of an intra-aorta pump

The intra-aorta pump is a novel left ventricular assist device (LVAD) that assists the heart without the need for percutaneous wires and conduits. It is implanted between the radix aortae and the aortic arch to avoid damage to the aortic valve. To predict the mean pressure head and blood flow, a nonlinear lumped parameter model, which does not need the parameters of the circulatory system, is established. The model includes a speed-controlled current source, an internal resistor, and an inductance for simulating the pressure-flow rate relationship. The speed-controlled current source is used to represent the blood flow caused by the kinetic energy from the impeller, the internal resistor is used to stimulate the resistance character of the radial clearance of the intra-aorta pump, and the inductance is used to model the inertia of the blood that passes through the radial clearance. Each part of the model has clear physical significance, which is helpful for extending the model to other blood pumps. It can generate all status of the pump from suction to pulmonary congestion. The model is summarized as a function of the pressure head, the blood flow, and rotational speed of which the values of parameters in the model are determined by experiment. The model and prediction method are tested experimentally on an in vitro mock loop. A comparison of the predicted pressure head obtained from our model with experimental data shows that our model can predict the differential pressure accurately with error <5% for all experimental conditions over the entire range of intended use of the intra-aorta pump.     

Robust motor speed control under time varying loads in moving actuator type artificial heart (AnyHeart)

The Moving Actuator type artificial heart(AnyHeart) as well as many other artificial hearts uses a motor as its power source. For controllability of control parameters such as pump rate, pump output, blood pressure profile and flow form, the precise motor speed control is important. However, because the implantable device has limited carrying capacity of hardware components in size and number, applying diverse motor control methods are not possible. In addition, the existing PI (Proportional-Integral) motor controller does not show satisfactory performance. A new controller that is sufficiently robust for the changes of load and physical system parameters has been designed and tested. The robust speed controller is based on the sliding mode control method that is applicable to a system of which the ranges of uncertainty in physical parameters are known. In a mock circulation system test, the actual speed showed good tracking characteristics in respect to the reference speed. Fast follow-up characteristics were also observed under high afterload and speed conditions. The speed error, current and power consumption were reduced by about 40%. The proposed control technique overcomes the limitations of the PI controller, and makes important improvements in both performance and stability.     

基于虚拟仪器技术的新型血液粘度仪的研制

目的:基于卡森方程的原理,设计发展出一种新型的快速准确测量血液粘度的仪器。方法:此种新的测量仪器基于有别于传统的磨擦力矩测量血液粘度的方法,其动态测量方法接近血液在血管中的流动性特点,且测量更为快速。根据血液具有非牛顿流体的特性,结合血液在平直圆管中的卡森流量公式,以及Stokes公式,通过一系列的数学推导,借助计算机虚拟仪器软件技术进行复杂的数学运算,求出血液的卡森粘度及卡森屈服应力。并以压力传感器和恒流蠕动泵,排废泵,锥形贮血瓶,清洗液瓶,五个电磁阀,及相应的管路和进样针等组成有关仪器系统。结果:通过数据信号采集板控制电磁阀与恒流蠕动泵的运行,实现了对血液卡森粘度及卡森屈服应力的简便快捷测定,并同时方便得出了在各种切变率下的血液表观粘度。结论:与现有临床同类仪器相比较,本文所研制出的血液粘度仪具有更简单的机械结构,更快的测量速度与相当高的精确性,其不仅能检测出全血等各种流体在任意不同切变率下的表观粘度,且能精确求出全血的卡森粘度及卡森屈服应力,具有重要的临床诊断意义。