• 대한의용생체공학회:의공학회지
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• 제28권4호
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• pp.449-454
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• 2007

An electrohydraulic (EH) pump-driven closed-loop blood pressure regulatory system was developed based on flow-mediated vascular occlusion using the vascular occlusive cuff technique. It is very useful for investigating blood pressure-dependant physiological variability, in particular, that could identify the principal mediators of renal autoregulation, such as tubuloglomerular feedback (TGF) and myogenic (MYO), during blood pressure regulation. To address this issue, renal perfusion pressure (RPP) should be well regulated under various experimental conditions. In this paper, we designed a new EH pump-driven RPP regulatory system capable of implementing precise and rapid RPP regulation. A closed-loop servo-controlwas developed with an optimal proportional plus integral (PI) compensation using the dynamic feedback RPP signal from animals. An in vivo performance was evaluated in terms of flow-mediated RPP occlusion, maintenance, and release responses. Step change to 80 mmHg reference from normal RPP revealed steady state error of ${\pm}3%$ during the RPP regulatory period after PI action. We obtained rapid RPP release time of approximately 300 ms. It is concluded that the proposed EH RPP regulatory system could be utilized in in vivo performance to study various pressure-flow relationships in diverse fields of physiology, and in particular, in renal autoregulation mechanisms.

• 한국임상수의학회지
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• 제36권6호
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• pp.325-329
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• 2019

This study was designed to compare the effects of continuous release of an anti-glaucoma drug applied by an osmotic pump and by conventional eye drop instillation in normal beagle dogs, by measuring drug concentration in the blood and monitoring intra-ocular pressure (IOP). In group 1, an osmotic pump filled with Trusopt® was implanted subcutaneously over the right eye of each dog and the IOP was measured. In group 2, the right eye of each dog was administered with 2% dorzolamide (Trusopt®, Merck, USA) three times per day. Blood was sampled once per week in all groups. The IOP of the end of this study was 16.7 ± 0.58 mmHg in group 2 and 17.7 ± 2.52 mmHg in group 2. Dorzolamide concentration in blood increased continuously over 4 weeks up to 585.8 ± 79.42 ㎍/L in group 1, and 747.3 ± 27.89 ㎍/L in group 2. We achieved satisfactory results in the osmotic pump group, which had a similar effect on IOP, and low fluctuations in IOP. Therefore, the results of this study should allow osmotic pumps to be consider as an alternative method to eye drops for the effective, safe, and convenient treatment of glaucoma.

• 대한의용생체공학회:의공학회지
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• 제22권4호
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• pp.349-358
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• 2001

A novel electro-mechanical implantable ventricular assist system is developed as a bridge to transplantation or recovery for patients with end-stage heart failure. The developed system is composed of an implanted blood pump, an external monitoring system which stores data, and a wearable system including a portable external driver and a portable power supply system. The blood pump is designed to be implanted into the left upper abdominal space and provides blood flow from the left ventricular apex to the aorta. The pulsatile blood flow is generated by a double cylindrical cam. There was mo excessive heat emission from the blood pump into the temperature-controlled chamber in the heat test and no stagnated flow within the blood sac by the observation in the flow visualization test. Animal experiments were performed using sheep and calves. The maximum assist flow rate reached 7.85L/min in the animal experiment. The evaluation results showed that the developed system was feasible for the implantable ventricular assist system. The long-term in vitro durability test and mid-term in vivo experiments are in progress and mow the modified next model is under development.

• 제어로봇시스템학회논문지
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• 제8권12호
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• pp.1061-1065
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• 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.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.139-150
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• 1989

새로운 형태의 인공심장용 전동기구동형 혈액동기구동행 혈액 펌프플 개발하였다. 개발된 혈액 펌프는 소형, 고출력, 브러쉬 없는 직류 전동기를 에너지 변환 장치로 사용하였으며, 이 전동기 자체가 원호 형태의 궤적을 따라 좌우로 회전하도록 고안되었으며, 전동기를 포함한 '회전원통'의 웅직임이 좌우에 부착되어 있는 폴리우레탄으로 제작된 혈액 주머니를 번갈아 밀게 되어 혈액을 박출하게 된다. 본 연구에서 도입한 이동형 작동기 원리에 의해 다른 전동기 구동형 혈액 펌프가 안고 있는 두가지의 중요한 문제점인 펌프 크기의 증가와 자연 심장과의 해부학적인 구조상 접합의 문제점들을 개선할 수 있었다. 또한 펌프의 효율과 전동기에 의한 시스템의 온도 상승, 그러고 펌프 내에 유입되는 유체에 대한 이론적 해석을 실시하였으며, 일련의 모의 순환 실험을 통해 실험 결과를 비교하였다. 개발된 펌프 시스템은 이식형 완전 인공 심장으로 사용하기에 충분한 심박출량(9 L/m)과 전부하에 민감한 반응, 그리고 기계적인 안정도를 보여 주었다.

• Journal of Chest Surgery
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• 제49권3호
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• pp.145-150
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• 2016

Background: Extracorporeal circulation (ECC) can induce alterations in blood viscoelasticity and cause red blood cell (RBC) aggregation. In this study, the authors evaluated the effects of pump flow pulsatility on blood viscoelasticity and RBC aggregation. Methods: Mongrel dogs were randomly assigned to two groups: a nonpulsatile pump group (n=6) or a pulsatile pump group (n=6). After ECC was started at a pump flow rate of 80 mL/kg/min, cardiac fibrillation was induced. Blood sampling was performed before and at 1, 2, and 3 hours after ECC commencement. To eliminate bias induced by hematocrit and plasma, all blood samples were adjusted to a hematocrit of 45% using baseline plasma. Blood viscoelasticity, plasma viscosity, hematocrit, arterial blood gas analysis, central venous $O_2$ saturation, and lactate were measured. Results: The blood viscosity and aggregation index decreased abruptly 1 hour after ECC and then remained low during ECC in both groups, but blood elasticity did not change during ECC. Blood viscosity, blood elasticity, plasma viscosity, and the aggregation index were not significantly different in the groups at any time. Hematocrit decreased abruptly 1 hour after ECC in both groups due to dilution by the priming solution used. Conclusion: After ECC, blood viscoelasticity and RBC aggregation were not different in the pulsatile and nonpulsatile groups in the adult dog model. Furthermore, pulsatile flow did not have a more harmful effect on blood viscoelasticity or RBC aggregation than nonpulsatile flow.

• 한국전산유체공학회지
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• 제20권3호
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• pp.79-86
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• 2015

A blood pump is an important part of a cardiac assist device. Since the shear rate in blood is known to be a primary factor on hemolysis generation, it has been very important to evaluate hemolysis inside blood pumps for understanding performance and reliability of cardiac assist devices. In this study, hemolysis generation inside blood pumps is analyzed using CFD with power-law based models for the blood damage index(BDI), in order to overcome difficulties in measuring hemolysis by experiment. The BDI values in blood pumps can be evaluated using Lagrangian or Eulerian approaches. In this study, several Lagrangian and Eulerian approaches are compared to estimate the efficiency of the numerical methods in a practice sense. It is found that the Eulerian approaches are advantageous in terms of the efficiency and robustness. Two different Eulerian approaches are used to evaluate the BDI values of a few commercial blood pumps. For the conditions of extracorporeal membrane oxygenator(ECMO) and ventricular assist device(VAD), local generation of hemolysis is analyzed using divided regions of blood pumps, in order to investigate the effects of the pump geometry.

• 한국전산유체공학회지
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• 제20권2호
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• pp.88-95
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• 2015

Blood pump analysis process includes both mechanical and bio-mechanical aspects. Since a blood pump is a mechanical device, it has to be mechanically efficient. On the other hand, blood pumps function is sensitively related to the blood recirculation; hence, bio-factors such as hemolysis and thrombosis become important. This paper numerically investigates the mechanical and bio-mechanical performances of the Rotaflow in the extracorporeal membrane oxygenation(ECMO), Ventricular Assist Device(VAD), and full-load conditions. The operational conditions are defined as(400[mmHg], 5[L/min.]), (100[mmHg], 3[L/min.]), and (600[mmHg], 10[L/min.]) for ECMO, VAD, and full-load conditions, respectively. The results are presented and analyzed from the mechanical aspect via performance curves, and from bio-mechanical aspect via focusing on hemolytic characteristics. Regions of top and bottom cavities show recirculation in both ECMO and VAD condtions. In addition, Eulerian-based calculation of modified index of hemolysis(MIH) has been investigated. The results demonstrate that the VAD condition has the least risk of hemolysis among the others, while the full-load condition has the highest risk.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1869-1875
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• 2001

The paper presents computational and flow visualization results on a centrifugal blood pump. 4 impeller designs were tested at a rotational speed of 2000 rpm using blood analog as working fluid. All impellers have seven blades but of different geometry (Impellers A3, A4, B2 and R7). Flow visualization within the impeller passages was conducted using an image de-rotation system. A pair of large scale vortices was found within the blades of impeller R7 while a single vortex was found in most of the passages of backward facing impellers (Impellers A3, A4 and B2). To establish the effects of blade geometry on blood cells, CFD was used to simulate the blade to blade flow to provide an estimate of the maximum shear stress. The results showed that though most of the stresses within the blade passages are below a threshold level of 150 N/m$^2$for extensive erythrocyte damage to occur, there are some regions near to the leading edge of the pressure side where the shear stresses a abode threshold level.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.915-918
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• 2016

의료산업의 급속한 변화와 의료 및 간호 인력의 증가로 인하여 가상 시험 장치에 대한 개발이 요구되고 있으며 심장 모델링할 수 있는 시뮬레이터와 혈관, 혈류에 대한 실습장비에 대한 개발의 중요성이 증가하고 있다. 따라서 본 연구에서는 스텝 모터를 이용하여 심장 펌프를 제작하여 동맥과 정맥 혈압, 혈류 시뮬레이션을 위한 장비를 개발하고 그 기능을 평가하고자 한다. 제안 시스템은 심장 시뮬레이션을 위한 펌프와 동맥, 정맥 혈관의 저항을 모사하기 위한 밸브장치 그리고 정맥계의 특성을 나타내는 저감장치로 구성한다. 심장 시뮬레이터는 롱거펌프(BOXER)를 사용하였으며 동맥과 정맥혈관은 실리콘 튜브를 사용하고 저감장치를 설계 및 제작하였다. 그리고 동맥혈압 측정을 위하여 압력센서를 사용하였다. 또한 제안 시스템의 평가를 위하여 심장 박동수는 분당 60회로 혈압의 범위는 50 ~ 100mmHg로 선정하여 측정 혈압과 사람의 혈압을 비교 평가하였다.