基于CFD的离心式人工心脏泵的溶血预测方法

溶血的定量评价对于人工心脏泵的设计和研究十分重要.本研究应用CFD（computational fluid dynamics）技术,针对两种叶轮设计的离心血泵进行了数值模拟,计算得到了其内部的流线分布.根据溶血、切应力和暴露时间三者之间的幂函数模型,对血泵的溶血进行了预测.最后,用溶血实验结果进行了验证.结果表明,在相同的边界条件下,流线型叶轮泵内的溶血值要小于直叶片叶轮泵,与溶血实验结果一致.可见,应用CFD实现溶血的定量计算是可行的,溶血、切应力和暴露时间之间的幂函数模型能较好地反映血泵的溶血性能.     

混流式血泵的数值模拟及性能分析

轴流式血泵转速过高、离心式血泵容易产生流动死区是造成血液损伤的重要原因,而混流式血泵能有效缓解轴流式血泵的转速过高以及离心式血泵的流动死区问题。基于此,本研究旨在探究闭式叶轮混流式血泵的性能效果。通过数值模拟的方法对闭式叶轮混流式血泵进行数值模拟,分析该类型血泵的流场特性及压力分布情况,探讨其水力性能以及可能对红细胞造成的损伤程度,并与半开式叶轮结构混流式血泵的数值模拟结果进行性能对比。结果表明:本研究中的闭式叶轮混流式血泵具有良好的性能,能够安全高效运行。该泵在5 L/min下能够达到100 mm Hg的扬程,血泵内流动均匀,没有明显的涡流、回流以及流动停滞现象,压力分布均匀合理,可有效地避免血栓;溶血指数平均值(HI)为4.99×10^-4,具有良好的血液相容性;与半开式叶轮混流式血泵相比,闭式叶轮混流式血泵扬程和效率更高、溶血指数平均值更小,且具有更好的水力性能及避免血液损伤的能力。通过本文研究结果,或能为闭式叶轮混流式血泵的性能评价提供依据。     

血泵驱动电机的生理控制策略研究

目的在分析现有血泵电机驱动控制策略的基础上,以外磁场驱动轴流式血泵为研究对象,提出基于心室功的血泵驱动电机控制策略,使血泵的输出控制模拟心脏输出的工作机制,提高受体的生活质量。方法建立主动脉瓣处包含血液动力学参数的压力和流量方程,设计了血泵的控制系统及实现方法;以常态和病态血液动力学参数作为例子,对控制目标模型进行仿真;实验严格控制系统的可行性。结果不论是常态还是病态,主动脉瓣处仿真压力与临床数据基本相符;血泵电机的输出与控制目标模型相符,控制系统的响应满足控制性能的要求。结论以心室功作为血泵的控制目标容易满足受体的生理要求,使血泵电机运行在最佳工作状态,为基于生理机制的血泵控制提供一种方法。     

高速螺旋流场中人体血液流动性能及红细胞力学行为分析

血泵的溶血程度主要受血液的运动流场影响,所以研究血液在血泵内腔的螺旋流动特性对于螺旋叶片血泵的设计和研究工作具有十分重要的意义。本文将血液流变理论和传统的力学分析方法相结合,对血液在低、高剪切变率两种条件下的环形空间螺旋流动性能进行了研究,给出了速度表达式,分析了各参数对流动性能的影响,同时还对高速螺旋流场中红细胞的力学行为进行了分析。结果表明,高速螺旋流场中的血液流动情况十分复杂,在进行高速螺旋血泵设计时,应综合考虑血液在不同剪切变率条件下的流动性能及红细胞的力学行为。     

基于热流耦合的轴流式血泵温升影响因素研究

人工心脏已进入临床发展阶段，溶血现象是制约人工心脏长久使用的一大难题。不正常的温度条件会使红细胞的正常生理机能和形态发生改变，从而影响其携氧能力。为研究人工心脏正常运转时的温升情况，先利用Solidworks软件建立轴流式血泵的三维仿真模型，然后基于ANSYS Workbench软件对血泵整体进行热流耦合温度场仿真，探究了定子绕组相阻值、血泵转速、定子外壳和泵外壳之间的气隙导热系数以及血液导热系数对血泵及血液整体温升的影响。结果表明，在满足血泵供血要求的前提下，适当减小定子绕组相阻值、降低转速可有效降低血泵整体温升，而气隙物质和血液导热系数的变化对血泵整体温度的影响不是很明显。     

介入式微型轴流血泵溶血机理及影响因素分析

溶血性能是判别血泵是否可靠的重要评价因素之一,也是血泵研发过程中的一大难题。本文基于介入式微型轴流血泵的结构特点对其溶血发生机理和关键影响因素进行探究和综述。首先,介绍介入式微型轴流血泵的结构特点:体积小、转速高、叶轮轮缘与泵壳间隙小。然后从剪力溶血和空化溶血两个方面对溶血发生机理进行阐述。最后重点分析导致介入式微型轴流血泵机械溶血的主要力学因素,即剪力和负压。泵内剪力过大或作用时间过长会导致红细胞受损而发生溶血,而负压可能引起血泵空化从而对血液造成损伤。总之,血泵结构设计不当会导致血液在机械运动和湍流运动过程中受到高剪切应力和局部负压的作用产生溶血,所以在设计阶段应全面考虑各因素对血泵溶血的影响。     

轴流式血泵的研究进展

轴流式血泵作为一种左心室辅助装置,对于心脏病患者尤其是等待移植的重症患者,具有重要的意义.本文介绍了目前世界上最流行的8种轴流式血泵的设计参数、实验结果以及临床应用现状,并对其发展前景进行了展望.     

基于CFD的液悬浮人工心脏泵叶轮入口优化分析

目的应用计算流体动力学方法(computational fluid dynamics,CFD)对离心式双向液力悬浮人工心脏血泵流场进行仿真分析,通过改进叶轮入口结构来改善血液在血泵的流动状态,从而提升其抗溶血性能。方法从影响血泵溶血性能的角度考虑,基于N-S方程和k-ε标准双方程湍流模型,应用软件FLUENT6.3对离心式人工心脏血泵流场进行数值模拟,分析在设计工况下,叶轮入口处的结构变化对泵内流场的影响,以及流场中最大速度与溶血水平之间的关系,并根据流场分析结果对血泵叶轮入口进行优化。结果经过优化,血泵内流场紊乱现象得到改善,影响溶血值的切应力和曝光时间均有所降低,溶血性能得到改善。同时,对于离心式双向液力悬浮血泵,在设计工况下,其流场中最大速度有作为流场优化过程中的直观指标参数的潜力。结论该研究的仿真分析可为离心式双向液力悬浮人工心脏的设计积累一定经验。     

血泵溶血的研究进展

国内外研究人员为克服溶血问题做了大量的工作,对血泵溶血性能作出了评价标准,通过利用实验和仿真手段对可能造成溶血的因素,如血泵结构、叶轮参数、血泵材料、血泵流场分布等做了很多的研究,分析了这些因素与血泵溶血的关联性,从而为在一定程度上解决血泵的溶血问题找到了方法.我们对目前血泵溶血的研究进行了综述.     

螺旋血泵的CFD分析

溶血和血栓是目前国内心室辅助装置不能应用于临床的主要原因。血泵的不良血液动力学特性是导致溶血和血栓的主要因数。计算流体力学（CFD）方法目前被广泛应用于血泵设计,它可以准确有效地反映血泵内部流场状态、血泵压力流量曲线以及血泵内部流场剪切力分布状态等。本研究采用CFD方法对自制螺旋血泵的泵腔、出入流口进行流场分析,内部流场采用三维彩图显示。结果显示CFD分析结果很好的与体外实验结果吻合。血泵血液动力学特性,以及内部血流状态采用CFD方法分析,可以有效地分析血泵血液相溶性方面的问题。     

磁液悬浮离心血泵体外溶血的实验及耐久性实验

通过建立模拟循环管路系统来研究磁液悬浮离心血泵的溶血性能及机械稳定性。建立体外模拟循环管路系统,体外溶血实验中以新鲜羊血为循环介质,调节前负荷和后负荷分别为15、100 mmHg,血泵转速设定为2 900 rpm,测定血浆游离血红蛋白含量（FHb）和红细胞压积（Hct）,计算血泵标准溶血指数（NIH）;耐久性试验其他各项设定同体外溶血实验,循环介质改为甘油水溶液。在体外溶血实验中,测得磁液悬浮离心血泵NIH值为（0.0038±0.0008）g/100L;耐久性实验中血泵连续正常运转90 d,期间无卡壳、停泵等现象,电压、电流、转速稳定。该血泵溶血性能处于较高水平,机械性能稳定可靠,满足进一步进行动物实验的要求。     

Optimization of a miniature Maglev ventricular assist device for pediatric circulatory support

A miniature Maglev blood pump based on magnetically levitated bearingless technology is being developed and optimized for pediatric patients. We performed impeller optimization by characterizing the hemodynamic and hemocompatibility performances using a combined computational and experimental approach. Both three-dimensional flow features and hemolytic characteristics were analyzed using computational fluid dynamics (CFD) modeling. Hydraulic pump performances and hemolysis levels of three different impeller designs were quantified and compared numerically. Two pump prototypes were constructed from the two impeller designs and experimentally tested. Comparison of CFD predictions with experimental results showed good agreement. The optimized impeller remarkably increased overall pump hydraulic output by more than 50% over the initial design. The CFD simulation demonstrated a clean and streamlined flow field in the main flow path. The numerical results by hemolysis model indicated no significant high shear stress regions. Through the use of CFD analysis and bench-top testing, the small pediatric pump was optimized to achieve a low level of blood damage and improved hydraulic performance and efficiency. The Maglev pediatric blood pump is innovative due to its small size, very low priming volume, excellent hemodynamic and hematologic performance, and elimination of seal-related and bearing-related failures due to adoption of magnetically levitated bearingless motor technology, making it ideal for pediatric applications.     

基于溶血性能的离心式旋转血泵设计

溶血性能是衡量血泵性能的一个重要指标.基于平均剪切应力模型,通过减少红细胞流经叶轮的时间和降低它在此过程中所受平均剪切应力的方法,对离心血泵进行设计,进而改善溶血性能.采用商用流体仿真软件Fluent,对血泵内的三维不可压湍流流场进行数值模拟,得到红细胞在血泵内的流动迹线和流动参数;应用溶血估算公式,分析不同流量下血泵的溶血性能,计算得到溶血估算值在0.006-0.015之间,有较好的溶血性能,满足血泵对溶血性能的要求.     

Computer assisted design for the implantable left ventricular assist device (LVAD) blood pump using computational fluid dynamics (CFD) and computer-aided design and manufacturing (CAD/CAM)

Thrombus formation and hemolysis are critical issues in the design of a long-term implantable LVAS (left ventricular assist system). The fluid dynamic characteristics of the blood flow are one of the main factors that cause thrombus formation and hemolysis. In this study, we optimized blood chamber geometry, port design, and fluid dynamics in our implantable LVAS to ensure minimization of shear-stress-related blood damage. A blood pump chamber (stroke volume, 65 ml) and an inflow and outflow port were designed with three-dimensional CAD (computer-aided-design) software (Pro-Engineering version 20) and estimated by FEM (fine-element method) computational fluid dynamic (CFD) analysis (Ansys version 5.5). We adopted three-dimensional distribution of CFD results for qualitative evaluation, and we also tried to estimate the normalized index of hemolysis (NIH) and time-series change of hematocrit from the results of CFD analysis as quantitative index of optimization for geometry of the blood pump chamber. With the use of this design, the blood pump geometry was optimized as the decrease of NIH from 2.72 g/1001 in the first model to 0.098 g/1001 in the second model, corresponding to the decrease in shear stress. The hematocrit also improved from 0.7% in the first model to 11.5% in the second model 2 years after implantation of the pump. Areas where flow stagnation was observed in the first model were free of stagnation in the second model. The results show that computer-aided design of the blood pump contributes to optimizing a blood pump chamber for reducing thrombus formation and hemolysis, and also contributes to reducing cost and time in developing the implantable LVAS.     

五种叶轮血泵体外溶血试验的研究

血泵的标准溶血指数反映了它对血液的破坏程度，是衡量血泵性能的一个重要指标，选用I型离心，II型轴流，磁耦合，I型和II型螺旋混流5种叶轮血泵，用新鲜抗凝羊血500ml，平均压力100mmHg，流量5L／min,在转泵0，0．5，1．0…4．0h后，测量血浆游离血红蛋白含量和血泵出口处的表面温度，计算标准溶血指数。结果表明，5种血泵的转速，温度变化与溶血指数是没有直接关系的，由结构形成的运动流场是对血液造成破坏的主要原因。本文对5种血泵的温度变化，转速和溶血之间的关系做一探讨。     

Performance of a newly developed implantable centrifugal blood pump

The performance of the newly developed implantable centrifugal blood pump was investigated in vitro. The pump was developed with the end goal of building a versatile system that includes a left ventricular assist system with an internal secondary battery or an implantable biventricular assist system with two implantable blood pumps. The hydrodynamic characteristics and efficiency of the blood pump were evaluated, and the mechanical damage to the blood caused by the blood pump was assessed through a hemolysis test using fresh goat blood. The pump could generate 120 mm Hg at a flow rate of 5 L/min and a motor speed of 2,500 rpm. The electric input power to the pump was approximately 5 watts under these working conditions. The hemolysis caused by the pump was a bit higher than that by the former model, but stayed within an acceptable range. Performance of the pump in vitro was considered sufficient for a left ventricular assist device, although further design improvement is necessary in terms of hemolysis and system efficiency to improve biocompatibility of the pump.     

磁悬浮离心式心室辅助装置的体外溶血测试**

背景：心室辅助装置已广泛应用于心力衰竭患者的治疗。虽然有不同的血泵在国外应用于临床,却很少在国内应用,主要原因是其价格太高。因此在国内研制相对价格较低的能应用于临床的自主血泵迫在眉睫。 目的：测试置入式磁悬浮离心心室辅助装置主体血泵的溶血性能。 方法：通过计算流体力学方法,对磁悬浮离心式心室辅助装置主体血泵内部流场做初步分析。血泵在后负荷100 mm Hg     (1 mm Hg=0.133 kPa)、流量5 L/min 情况下,通过体外模拟血循环系统驱动羊血测试血泵体外溶血性能,计算血泵实际标准溶血指数NIH。 结果与结论：在设计工况下计算流体力学结果显示血泵内部流线平稳,整个流道内部壁面剪切力均在68.5 Pa以下,内部静压力分布均匀,过渡平稳,没有不良区域出现。体外溶血实验测得标准溶血指数NIH值为(0.075±0.017) mg/L。提示血泵驱动叶片及内部流道设计合理,同第3代血泵相比有较好溶血性能。血泵实验期间无不良状况发生,可以进行下一步长期的动物体内实验,进而评估血泵体内血流动力学性能和血泵置入对实验动物脏器的影响。     

Cardiopulmonary bypass system-mountable anesthetic machine

Miniaturization of the cardiopulmonary bypass (CPB) system may provide several benefits, such as decreasing the manpower, cost, and amount of homologous blood required and improving patient care. We have proposed a portable CPB system-mountable anesthetic machine. Our portable CPB system consists of a bypass circuit, a hard shell reservoir, a membrane oxygenator, and two pumps. The reservoir has three chambers, one venous and two suction chambers. These three chambers can control the negative pressure when connected with an ordinary vacuum system in the operating room. Pumps are used for perfusion and blood transfer from suction to venous chamber. We have been working to create a newly designed pump for this system. This pump consists of a polycarbonate rotor with six polyurethane vanes and acrylic acid resin housing. The housing is narrowed at both the inflow and outflow ports. This pump has characteristics of a vane pump as well as a friction pump. By using a DC brushless motor, it is possible to perfuse from 0.1 to 10 l/min, under bench testing. Preliminary animal tests of its operation produced very satisfactory results. Regarding hemolysis, the plasma free hemoglobin level was below 80mg/dl after 4h of operation using two pumps. This low-cost disposable CPB system enables it to be used for the portable CPB system-mountable anesthetic machine.