Optimum selection of an implantable secondary battery for an artificial heart by examination of the cycle life test

An implantable secondary battery is one of the key components in a total artificial heart system. Because a 2 year cycle life is required, the cycle life of the secondary battery as well as its charge and discharge properties are important parameters for selection of an appropriate battery. We carried out cycle life tests on four kinds of rechargeable batteries (a Ni-MH secondary battery, a Ni-Cd secondary battery, a Li-ion battery with a graphite anode, and a Li-ion battery with a nongraphitizable carbon electrode) to determine their suitability as implanted back-up batteries. Each of the batteries was charge/discharge cycled at 37 degrees C to 39 degrees C using a charge current of 1 C ampere, and they were each fully discharged under either pulsatile discharge loads, which mimicked pulsatile operation, or a nonpulsatile load equivalent to the average of the pulsatile loads. The two Li-ion batteries made by different manufacturers both met the minimum requirement of cycle life of more than 1,500 cycles, considering safety coefficient regardless of the discharge pattern. In addition, the temperature increase of these Li-ion batteries (3 degrees C) was lower than that of Ni-Cd and Ni-MH batteries (15-25 degrees C). Out of these four batteries, the two Li-ion batteries are the most suitable for use in a totally implantable artificial heart system.     

Recording vagal nerve activity for the control of an artificial heart system

Monitoring cardiovascular control system information is important in considering the quality of life (QOL) of patients with artificial hearts. Natural heart circulation is controlled by an autonomic nervous system. Therefore, it is desirable to record autonomic nerve activity for the control of artificial heart systems. We directly recorded vagal nerve activity in long-term animal experiments. Six healthy adult goats were anesthetized with halothane inhalation, and thoracotomy was performed with the fourth rib resection during mechanical ventilation. Arterial blood pressure and right and left atrial pressures were continuously monitored with an inserted catheter. Cardiac output was measured by an electromagnetic flow meter attached to the ascending aorta. After the chest was closed, an incision was made in the left neck, and the left vagal nerve was separated. Stainless steel electrodes were inserted into the vagal nerve and fixed by a plasticizer. After the incision was closed, the goats were transferred to a cage and extubated after waking. Vagal nerve activity was measured using hemodynamic parameters when the animals were awake. Our results show that clear observation of autonomic nerve discharge was made through this experimental system for over 1 month. The tonus of the vagal nerve was significantly altered before body motion with hemodynamic changes, suggesting the possibility of prediction. These results suggest that information from autonomic nerves may help to control implantable artificial hearts or ventricular assist devices.     

Wireless patient monitoring system for a moving-actuator type artificial heart

In this study, we developed a wireless monitoring system for outpatients equipped with a moving-actuator type pulsatile bi-ventricular assist device, AnyHeart. The developed monitoring system consists of two parts; a Bluetooth-based short-distance self-monitoring system that can monitor and control the operating status of a VAD using a Bluetooth-embedded personal digital assistant or a personal computer within a distance of 10 meters, and a cellular network-based remote monitoring system that can continuously monitor and control the operating status of AnyHeart at any location. Results of in vitro experiments demonstrate the developed system's ability to monitor the operational status of an implanted AnyHeart.     

In vitro controllability of the MagScrew total artificial heart system

The purpose of this study was to evaluate the in vitro responses to preload and afterload of our total artificial heart (TAH), the MagScrew TAH. The TAH consists of two blood pumps and a control logic, developed at the Cleveland Clinic, OH, and the MagScrew actuator and its electronic control system, developed by Foster-Miller Technologies, Inc., Albany, NY. Tests were performed on a mock circulatory loop, using water as a test fluid. Preload sensitivity of the Mag-Screw TAH demonstrated a Frank-Starling response to preload in automatic mode. A peak flow of 10 L/min was obtained, with a left atrial pressure of 13 mm Hg. The relationship between right atrial pressure and left atrial pressure was well balanced when tested with a left bronchial shunt flow of 5% and a range of pulmonary artery and aortic pressures. With respect to afterload response, the left pump showed a relatively low sensitivity, which allowed the pump to maintain perfusion over a wide range of aortic pressures. The right pump, on the other hand, was much more sensitive to pulmonary artery pressure, which provided a measure of protection against pulmonary congestion. The very effective physiologic response of the MagScrew TAH is believed to result from employment of a left master, alternating ejection control logic, high inherent sensitivity of the blood pumps to atrial pressure, a lower effective stroke volume for the right pump, and a scaling of right side motor ejection voltage to 80% of that used for the left side ejection.     

Computerized hydrodynamic ″flow″ system for artificial heart valve testing

Scientific-Research Institute of Transplantation and Artificial Organs, Ministry of Health of the USSR, Moscow. Translated from Meditsinskaya Tekhnika, No. 6, pp. 30–32, November–December, 1990.     

Home care artificial heart monitoring system via internet

The availability of a remote management system, which provides both physiological-related information about the patient and device-related information about the implanted device, would be helpful during in vivo experiments or clinical trials involving artificial heart implantation. In order to be able to monitor the course of the in vivo experiment continuously regardless of the patient's location, an internet-based remote monitoring system was developed, which can monitor physiological-related information such as pressure (AoP, LAP, RAP, PAP) and flow data, as well as device-related information such as current, direction and pump operating conditions. The home care artificial heart monitoring system which we developed consists of four main components, which are the transcutaneous information transmission system (TITS), local monitoring station (LMS), data server station (DSS), and client monitoring station (CMS). The device-related information and physiological-related information can be transmitted in real time from a patient in a remote non-clinical environment to the specialist situated in a clinic depending on the current capabilities and availability of the internet. The local monitoring station situated at the remote site is composed of a data acquisition and preprocessing unit connected to a computer via its RS-232 port, and which communicate using a Java-based client-server architecture. The remote monitoring system so developed was used during an in vivo experiment of the artificial heart implantation for 2 months and performed successfully according to design specifications.     

Design of a new artificial breathing system for simulating the human respiratory activities

The purpose of this work is the conception and implementation of an artificial active respiratory system that allows the simulation of human respiratory activities. The system consists of two modules, mechanical and electronical. The first one represents a cylindrical lung adjustable in resistance and compliance. This lung is located inside a transparent thoracic box, connected to a piston that generates variable respiratory efforts. The parameters of the system, which are pressure, flow and volume, are measured by the second module. A computer application was developed to control the whole system, and enables the display of the parameters. A series of tests were made to evaluate the respiratory efforts, resistances and compliances. The results were compared to the bibliographical studies, allowing the validation of the proposed system.     

心脏瓣膜双轴力学特性测试系统的设计

目的为了获得心脏瓣膜力学特性,设计一套高精度双轴拉伸机系统。方法采用上、下位机结构。上位机采用Labview软件编程,设计人机界面,提高系统灵活性和数据处理能力;下位机采用数控语言编程,提高用户编程的简易性和灵活性;采用灵敏度1μm的机械运动硬件模块、16位数据采集卡、光学位移测量方法,提高系统测量精度。对猪的二尖瓣前瓣进行双轴拉伸实验,并将实验结果与国外研究者测试数据进行对比。结果猪二尖瓣前瓣的应力-应变数据与国外研究者测试数据差别为0.4%~3.7%。结论本系统可灵活地对心脏瓣膜和其他生物软组织进行力学特性测试。     

Clinical utilization of the artificial heart

During the past 30 years the artificial heart has evolved from a bioengineering concept to clinical reality. To date four patients have had an artificial heart implanted as a permanent device, while over 150 artificial hearts have been utilized temporarily as a bridge to cardiac transplantation. Increased use of this device requires that a number of issues be critically addressed: (1) criteria for patient selection; (2) operative techniques for implantation including size of device and its position in the mediastinum; and (3) management of the patient in the intensive care unit (ICU), in particular, regimens of anticoagulation, assessment of adequacy of organ perfusion, and prevention of sepsis. This chapter is a discussion of these bioengineering and clinical concerns with respect to the Jarvik total artificial heart (TAH). Clinical data are presented which highlight the current problems with these devices and the areas of future research that need to be undertaken.     

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．     

Operating point control system for a continuous flow artificial heart: in vitro study

We proposed and developed a practical and effective servo control system for rotary blood pumps. A rotary blood pump for assisting the failing natural heart should be operated only in physiologically acceptable conditions. The operation of a rotary blood pump is based on the rotational speed of the impeller and pressure head. If the pump flow and the pressure head are set within an acceptable range, the driving condition is deemed normal condition, and this control system maintains the preset operating point by applying proportional and detective control (PD control). If the pump flow or pressure head is outside the acceptable range, the driving condition is determined to be abnormal condition, and this system operates the pump in a recovery fashion. If the driving condition is kept under abnormal conditions of sudden decrease of the flow, the condition is termed a suction condition. The controller releases the pump from the suction condition and later returns it to the normal condition. In this study, we evaluated these servo control modes of the centrifugal pump and confirmed whether the performance of this proposed operating point control system was practical.     

基于Windows XP环境的人工心脏瓣膜脉动流检测系统设计与实现

本文着重论述了人工心脏瓣膜脉动流检测仪控制系统的数据采集、处理、计算、分析,并对数据库进行了改进,将操作系统升级为Windows XP,开发语言为Visual Basic 6.0、Access 2000,经过调试,实际测试获得了良好结果.     

Noninvasive assessment method to determine the anatomic compatibility of an implantable artificial heart system

To assess the anatomic compatibility of an artificial heart (AH), we attempted to develop a computer environment that would facilitate a reliable simulation of an AH implanted in the human thorax. A three-dimensional thoracic computer model with a ventricle-resected heart was constructed, by using manually extracted contour points of the aorta, pulmonary artery, atria, atrioventricular valves, diaphragm, and thoracic wall from a set of consecutive CT images. Such a model enabled simulation of an AH implantation by orienting the AH model in it. Error evaluation on CT imaging and contour extraction with a Plexiglas cylindrical phantom showed that the diameter of the extracted phantom contour was approximately 2 mm smaller than its original with a standard deviation of <0.5 mm. Errors in contour and surface reconstruction could be reduced to far less than 1 mm under constrained conditions. A study on the influence of breathing revealed that variations in some thoracic dimensions between inspiration and expiration could reach 10 mm. In summary, computer simulation of AH implantation is a worthwhile approach with acceptable accuracy, although further considerations of extreme thoracic situations will be required.