• Journal of Chest Surgery
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• v.29 no.7
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• pp.689-699
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• 1996

An animal experiment was designed for the evaluation of in vivo performance of the newly developed electrohydraulic type ventricular assist device and its influence on the left ventricular function during pal- satile left ventricular assist. Eight adult sheep were incorporated into the study and data were collected from seven sheep. Total as- sist time ranged from 69 minutes to 7 days. The performance of the device was satisfactory both in asyn- chr nous and synchronous mode within the range of given native heart rate. More than 4 liters of device output could be reached within the range of normal left atral pressure without development of negative pressure in the left atrium. Moderate to severe degree of hemolysis was noted as evidenced by significant increase of plasma free hemoglobin level after 3 days of left ventricular support along with the presence of the small amount of thrombi around the floating disc type polymer valve apparatus reflecting that further study and refinement of the device need to be done in regard of biocompatibility and thromboresistance. The hemodynamics showed increase in heart rate (p < 0.05), cardiac output and left ventricular minute work (p < 0.05) after placement of the device at the flow rate of 2.0∼2.5 Llmin. The left atrial pressure, left ventricular pressure and LV dpldt were decreased after the device placement(p < 0.05). The endocardial viability ratio and oxygen contents of the mixed ven us blood and coronary venous blood were all increased (p < 0.05) after the device placement suggesting effective unloading of the left ventricle was accomplished. The myocardial perfusion was thought improved in synchronous counterpulsation as suggested by sig- nificant increase in endocardial viability ratio and coronary venous blood oxygen content in synchronous assist mode comparing with asynchronous mode.

• Proceedings of the KTCVS Conference
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• 1998.10a
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• pp.3-3
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• 1998

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.83-90
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• 1998

In this paper, we present neural network for control of Left Ventricular Assist Device(LVAD) system with a pneumatically driven mock circulation system. Beat rate(BR), Systole-Diastole Rate(SDR) and flow rate are collected as the main variables of the LVAD system. System modeling is completed using the neural network with input variables(BR, SBR, their derivatives, actual flow) and output variable(actual flow). It is necessary to apply high perfomance control techniques, since the LVAD system represent nonlinear and time-varing characteristics. 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 and control the LVAD system by PID controller and neural network feedforward controller. The ability and effectiveness of controlling the LVAD system using the proposed algorithm will be demonstrated by experiment.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.211-215
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• 1995

전기유압식 좌심실 보조장치에서 모터 전류 파형을 정보로 하여 작동기의 이완기 속도를 조절함으로써 좌심방으로부터 유입되는 혈류량을 조절하는 알고리즘을 개발하였다. 전기 유압식 좌심실 보조장치에서는 혈액의 유입이 능동적으로 이루어지므로, 좌심방 함몰로 인한 심근 손상 및 외부 공기 유입으로 인한 색전증을 방지하기 위해 유입혈류량을 현재 좌심방 내의 상태에 따라 적절히 조절해 주어야 한다. 좌심방 내의 혈액량 정도는 혈액을 유입해내는 작동기의 이완기 동작 시에 소모되는 에너지 크기에 반영되고, 작동기를 구동하는 모터에 들어가는 전류의 크기는 작동기에 공급되는 에너지에 비례하므로, 이 전류 파형의 정보들을 통해 좌심방 내의 상태를 추정해 볼 수 있다. 본 논문에서는 퍼지로직을 적용하여 모터 전류 파형의 이상 유무를 판단한 뒤 이에 따라 작동기의 이완기 속도를 조절하는 알고리즘을 개발하여 모의순환장치 실험을 통해 그 실효성을 검증한 결과를 정리하였다.

• Journal of Chest Surgery
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• v.34 no.5
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• pp.403-406
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• 2001

본 증례는 66세(51.8kg)된 남자에서 수술전 심한 좌심실 기능 부전과 승모판 및 삼첨판 폐쇄부전이 있어 개심술 시행후 심한 저심박출증 발생으로 인공심폐기 이탈에서 실패하고 양심실 보조장치(Centrifugal Biopump)를 사용한 후 이로부터 성공적인 이탈과 퇴원이 보고하는 바이다.

• Journal of Chest Surgery
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• v.27 no.5
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• pp.390-393
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• 1994

의료기술의 발달로 오늘날의 개심술은 대부분 성공적으로 시행되고 있지만 극히 일부분은 아직도 개심술후 심한 심실기능의 저하로 사망하는 겨우가 있다. 1960년대 중반 Spencer와 DeBakey에 의해 개심술후 심한 심실기능이 저하된 환자에게 심실보조장치를 이용하여 성공적으로 치험한 이후로 많은 발전을 거듭해 왔다. 저자들은 4개월 (6.5Kg)된 남아에서 개심술후 심한 저심박출증으로 인공심폐기의 제거를 못하여 좌심실 보조장치(Centrifugal Biopump)를 사용하여 성공적으로 치험하였기에 보고하는 바이다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.22-28
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• 2013

It is important to begin left ventricular assist device (LVAD) treatment at appropriate time for heart failure patients who expect cardiac recovery after the therapy. In order to predict the optimal timing of LVAD implantation, we predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used LVAD-implanted cardiovascular system model which consist of 8 Windkessel compartments for the simulation study. The time-varying compliance theory was used to simulate ventricular pumping function in the model. The ventricular systolic dysfunction was implemented by increasing the end-systolic ventricular compliance. Using the mathematical model, we predicted cardiac responses such as left ventricular peak pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous and pulsatile LVAD. Left ventricular peak pressure, which indicates the ventricular loading condition, decreased maximally at the 1st level heart-failure under pulsatile LVAD therapy and 2nd level heart-failure under continuous LVAD therapy. We conclude that optimal timing for pulsatile LVAD treatment is 1st level heart-failure and for continuous LVAD treatment is 2nd level heart-failure when considering LVAD treatment as "bridge to recovery".

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

• Journal of Biomedical Engineering Research
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• v.23 no.1
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• pp.33-38
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• 2002

A Ventricular Assist Device(YAD) is used to support the injured natural heart So. when considering a control algorithm for YAD. it is important to reduce a natural heart's load to enhance its recovery condition. To reduce natural heart's load, a counterpulsation algorithm is used commonly. In this study, we developed a counterpulsation control algorithm for moving-actuator type VAD and tested its usefulness using in vitro MOCK circulatory system. To notice a natural heart's Pumping status, electrocardiogram(ECG) signal was used and as a result of test. the counterpulsation effect between YAD and a natural heart was occurred and Automatic Control Mode Transition was occurred properly.

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