• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.346-350
• /
• 1996

This paper presents a Neural Network Identification (NNI) method for modeling of highly complicated nonlinear and time varing human system with a pneumatically driven mock circulation system of Left Ventricular Assist Device(LVD). This system consists of electronic circuits and pneumatic driving circuits. The initation of systole and the pumping duration can be determined by the computer program. The line pressure from a pressure transducer inserted in the pneumatic line was recorded. System modeling is completed using the adaptively trained backpropagation learning algorithms with input variables, Heart Rate(HR), Systole-Diastole Rate(SDR), which can vary state of system, and preload, afterload, which indicate the systemic dynamic characteristics and output parameters are preload, afterload.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.11
• /
• pp.1205-1211
• /
• 2011

In this paper, we developed a pacemaker that can increase the efficacy of a left ventricular assist device (LVAD) and increase the survival rate for patients suffering end-stage heart failure. Because LVAD patients can experience arrhythmia, the pacemaker incorporated into the LVAD has the important role of sustaining sufficient blood circulation during arrhythmia. The electrode of the pacemaker is located at the apex of the left ventricle, where the VAD's inlet cannula is connected. This is efficient placement, in that the electrode can transmit electrical stimulation directly to the Purkinje fibers of the myocardium. The pacemaker can change the stimulation rate from 0 bpm to 191.4 bpm when a button is pressed on the external control module, and the pacemaker normally stimulates the heart at 60 bpm with 0.25 J of energy. We performed animal experiments to evaluate the performance and reliability of the combination of the LVAD and pacemaker. At pacemaker stimulation rates of 86.4 bpm, 100.2 bpm, 126.6 bpm, we recorded the ECGs, aortic pressures, and flow rates to analyze the heart loads.

• Journal of Chest Surgery
• /
• v.35 no.5
• /
• pp.329-335
• /
• 2002

Background: The surgical technique for biventricular assist device(BVAD) implantation has mainly consisted of cannulation procedures. A median sternotomy has been the technique of choice as it gives a surgeon an excellent exposure of the heart. However, considering that most patients require a future sternotomy or already have a previous sternotomy, sternotomy-related complication remains a major concern in BVAD implantation. Based on this consideration as well as the clinical experiences of conventional heart surgery, the authors have hypothesized that the cardiac chambers for BVAD cannulation can be approached from the right side of the heart. The purpose of this studs to develop a novel surgical technique of right thoracotomy for BVAD implantation in an animals study. Material and Method: For last two years, 16 (11 calves, 3 canines, and 2 sheep) out of 30 experimental animals with AnyHeart implantation underwent a right thoracotomy. The device was used as an implantable BVAD in 14 animals, a wearable BVAD in 1, and an implantable LVAD in 1. The chest cavity was entered through the 4th intercostal space or the 5th periosteal bed. As for the BVAD use, a right inflow cannula was inserted into the right atrial free wall and a right outflow cannula was grafted onto the main pulmonary artery. A left inflow cannula was inserted into the interatrial groove and a left outflow cannula was grafted on the innominate artery of the ascending aorta. The connecting tubes were brought out through the thoracotomy wound and connected to the pump located in the subcutaneous pocket at the right flank. Result: Except for the 5 animals for a lilting test or during the early learning curve, all recovered smoothly from the procedures. The inflow drainage allowed the pump output 6.5 L/min at the maximum with 3-3.5 L/min in an average. Of the survivors, there noted no procedure-related mortality or morbidity. Necropsy findings demonstrated the well-positioned cannula tips in the each cardiac chamber

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.9
• /
• pp.739-745
• /
• 2014

Although medication is given to heart disease patients, conventional medication alone is not sufficient to treat heart disease. However, it has been reported that left ventricular assist device (LVAD) transplantation is an effective bridge to heart transplantation by assisting cardiac function. This study used long-term animal testing and emergency situations with a bovine model (Holstein) and canine model (Labrador-retriever) to evaluate the biocompatibility of LibraHeart-I (LH-1), which is a bent-tube type of LVAD that was developed in a previous study. In the long-term animal testing with the bovine model, the subjects survived for 49 days with no irregularities observed in their complete blood cell counts or the vital sign tests that were carried out during the test period. In short-term animal testing with the canine model, it was observed that blood did not remain inside the LH-I even without power support from an external drive source. In this study, the biocompatibility of the LH-I that was developed in a previous study was verified by the ejection performance during long-term animal testing and emergency situations.

• Proceedings of the KOSOMBE Conference
• /
• v.1996 no.05
• /
• pp.207-212
• /
• 1996

We developed pneumatic blood pump and its driving system as a pediatric ventricular assist device. The blood pump is diaphragm type system and its blood contacting area is coated with Bio-Span. The driving unit Is consists of dual pumps, valves for the reliable blood pumping and its controller uses 80C196(Intel) as a main processor. The acute animal experiment was performed with dogs and its body weight is about 20 kg. The maximum cardiac output is about 2.1 l/min and the pressure and flow curves showed reliable operation as assist device.

• Journal of Chest Surgery
• /
• v.29 no.11
• /
• pp.1218-1222
• /
• 1996

The reported incidence of postcardiotomy cardiogenic shock not responding to conventional therapy is still 0.1 to 0.8%. For this group of patients, more aggressive form of circulatory support must be employed. Centrifugal pumps are a ventricular assist device most commonly used on this purpose, due to low cost and easy availability. Currently, however, clinical experience of centrifugal pumps as a ventricular assist device is rarely reported in Korea. From January 1992 to January 1996, 2986 patients underwent cardiac operations on cardiopulmonary bypass at Seoul National University Hospital. Refractory postcardiotomy cardiac failure requring ventricular support with a Biomedicus centrifugal pump developed in ten of these patients. There were eight men and two women, ranged in age from nine years to 77 years with a mean of 50$\pm$20 years. The primary surgical procedures consisted of isolated coronary revascularization in four patients, combined coronary revascularization and aortic valve replacement in two, aortic dissection repair in two, pulmonary embolectomy in one, and heart transplantation in one. Of the ten patients, five had left ventricular assistance, one had right ventricular assistance, and four had biventricular assistance. Duration of ventricular assistance ranged from 24 to 175 hours, with a mean of 76$\pm$51 hours. Seven patients were weaned from ventricular assistance, and four of them discharged. The causes of death for nonsurvivors were progressive cardiac failure in two patients and multiorgan failure, intractable ventricular fibrillation, irreversible brain injury, and mechanical problem, respectively, in the other four. Survival was not predicted by time on cardiopulmonary bypass, aortic cross-clamp time, or duration of ventricular support. Major complications included bleeding(7), renal failure(6), infection(3) and neurologic complication(2). These results indicate that a centrifugal pump can provide reasonably satisfactory short-term circulatory support.

• Journal of Institute of Control, Robotics and Systems
• /
• v.8 no.12
• /
• pp.1061-1065
• /
• 2002

Sensors need to be implanted to obtain necessary information for LVAS (Left Ventricular Assist System) operations. Size of the sensors can prevent them from being implanted in a patient and reliabilities of the sensors are questionable for a long term use. In this wort we utilize a developed pump model to estimate flow and pressure difference across the pump without implanted sensors and present a method to obtain the physiological variables as aorta pressure and left ventricle pressure from the pump model and pulsatility of flow estimate or pressure difference estimate. These estimated variables can be used for LVAS control as an index or indices.

• Proceedings of the KOSOMBE Conference
• /
• v.1994 no.05
• /
• pp.146-147
• /
• 1994

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.260-266
• /
• 1996

In this paper, we presents neural network identification and control of highly complicated nonlinear Left Ventricular Assist Device(LVAD) system with a pneumatically driven mock circulation system. Generally the LVAD system need to compensate nonlinearities. Hence, it is necessary to apply high performance control techniques. Fortunately, the neural network can be applied to control of a nonlinear dynamic system by learning capability. In this study, we identify the LVAD system with Neural Network Identification. Once the NNI has learned the dynamic model of LVAD system, the other network, called Neural Network Controller(NNC), is designed for control of a LVAD system. The ability and effectiveness of identifying and controlling a LVAD system using the proposed algorithm will be demonstrated by computer simulation.

• Journal of Institute of Control, Robotics and Systems
• /
• v.4 no.3
• /
• pp.315-320
• /
• 1998

In this paper, we present the PID control method for the controlling flow rate of highly complicated nonlinear Left Ventricular Assist Device(LVAD) with pneumatically driven mock circulatory system. Beat Rate (BR), Systole-Diastole Rate (SDR) and flow rate are used as the main variables of the LVAD system. System modeling is completed using the neural network with input variables (BR, SDR, their derivatives, actual flow) and an output valiable(actual flow). Then, as the basis of this model, we perform the simulation of PID control to predict the performance and tendency of the system and control the flow rate of LVAD system using the PID controller. The ability and effectiveness of identifying and controlling a LVAD system using the proposed algorithm will be demonstrated through computer simulation and experiments.