• Journal of Chest Surgery
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• 제54권2호
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• pp.81-87
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• 2021

Background: Artificial grafts such as polyethylene terephthalate (Dacron) and expanded polytetrafluoroethylene (ePTFE) are used for various cardiovascular surgical procedures. The compliance properties of prosthetic grafts could affect hemodynamic energy, which can be measured using the energy-equivalent pressure (EEP) and surplus hemodynamic energy (SHE). We investigated changes in the hemodynamic energy of prosthetic grafts. Methods: In a simulation test, the changes in EEP for these grafts were estimated using COMSOL MULTIPHYSICS. The Young modulus, Poisson ratio, and density were used to analyze the grafts' material properties, and pre- and post-graft EEP values were obtained by computing the product of the pressure and velocity. In an in vivo study, Dacron and ePTFE grafts were anastomosed in an end-to-side fashion on the descending thoracic aorta of swine. The pulsatile pump flow was fixed at 2 L/min. Real-time flow and pressure were measured at the distal part of each graft, while clamping the other graft and the descending thoracic aorta. EEP and SHE were calculated and compared. Results: In the simulation test, the mean arterial pressure decreased by 39% for all simulations. EEP decreased by 42% for both grafts, and by around 55% for the native blood vessels after grafting. The in vivo test showed no significant difference between both grafts in terms of EEP and SHE. Conclusion: The post-graft hemodynamic energy was not different between the Dacron and ePTFE grafts. Artificial grafts are less compliant than native blood vessels; however, they can deliver pulsatile blood flow and hemodynamic energy without any significant energy loss.

• Neonatal Medicine
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• 제17권2호
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• pp.201-206
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• 2010

목적: 최근 미숙아에서 동맥관 결찰 술 후 설명할 수 없는 혈역동학적 불안정성에 대한 보고가 되고 있어 극소저체중아에서 동맥관 결찰술 후 발생하는 혈역동학적 불안정성의 위험 요인 및 임상 양상에 대해 알아보고자 하였다. 방법: 2002년 1월부터 2008년 12월까지 고려대학교 의료원내 3개 병원의 신생아 중환자실에서 치료 받은 재태 32주 미만의 극소저체중출생아에서 동맥관 결찰술을 시행 받은 환아 18명을 대상으로 하여 의무기록을 후향적으로 조사, 분석하였다. 수술 중 또는 수술 후 문제로 인한 혈역동학적 불안정성 이외에 설명할 수 없는 심폐 기능의 저하로 인공 호흡기 의존도의 증가와 혈압의 하강 등이 관찰된 환자를 혈역동학적 불안정군(hemodynamic instability group, HI)으로 정의하였다. 결과: 연구에 참여한 18명의 환아들의 재태 주수는 $27^{+6}{\pm}1^{+6}$주, 평균 출생 체중은 951${\pm}$245 g이었다. HI군은 7명(7/18, 39%)이었으며 혈역동학적 안정군(hemodynamic stability group, HS)은 11명(11/18, 61%)이었다. HS군에 비해 HI군은 출생 체중(1,033${\pm}$285 g vs. 821${\pm}$126 g, P=0.048)과 수술 시 체중(1,195${\pm}$404 g vs. 893${\pm}$151 g, P=0.042)이 작았으며, 재원기간이 길었고 (105${\pm}$29 vs. 141${\pm}$39, P=0.038) 심한 기관지 폐 이형성증의 빈도가 높았고(no/mild/moderate/severe, 2/5/2/2 vs. 0/1/2/4, P=0.038) 수술 전 $FiO_2$의 농도가 높았다(0.29${\pm}$0.06 vs. 0.38${\pm}$ 0.09, P=0.02). 18명 중 HS군에서 1명의 환아가 동맥관 결찰술 후 94일 째 패혈증으로 사망하였다. 결론: 극소저체중아에서 동맥관 결찰술 후 혈역동학적 불안 정성이 발생한 경우는 약 39%였다. 작은 출생 체중과 수술 시 체중, 수술 전 높은 산소 분압의 산소 투여가 동맥관 결찰술 후 혈역동학적 불안정성 발생의 위험인자가 될 수 있으며 아울러 혈역동학적 불안정성은 기관지 폐 이형성증의 유병률 및 중증도와 재원기간을 증가시킬 수 있음을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.59.2-59.2
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• 2005

• Journal of Chest Surgery
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• 제28권5호
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• pp.437-442
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• 1995

We developed an experimental model of brain death using dogs. Brain death was caused by increasing the intracranial pressure[ICP suddenly by injecting saline to an epidural Foley catheter in five female mongrel dogs[weight, 20-25Kg .Hemodynamic and electrocardiographic changes were evaluated continuously during the process of brain death. 1. Abrupt rise of ICP after each injection of saline followed by a rapid decline to a new steady-state level within 15 minutes and the average volume required to induce brain death was 7.6$\pm$0.8ml.2. Body temperature, heart rate, mean pulmonary arterial pressure, left ventricular[LV enddiastolic pressure and cardiac output was not changed significantly during the process of brain death, but there was an increasing tendency.3. Mean arterial pressure and LV maximum +dP/dt increased significantly at the time of brain death.4. Hemodynamic collapse was developed within 140 minutes after brain death.5. Marked sinus bradycardia followed by junctional rhythm was seen in two dogs and frequent VPB`s with ventricular tachycardia was observed in one dog at the time of brain death. Hyperdynamic state develops and arrhythmia appears frequently at the time of brain death. Studies on the effects of brain death on myocardium and its pathophysiologic mechanism should be followed in the near future.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.717-720
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• 2002

The present study is to evaluate the performances of flow velocity and wall shear stress in the stenosed coronary artery using human in vivo hemodynamic Parameters and computer simulation. Initial and follow-up coronary angiographics in the patients with angulated coronary stenosis are performed. Follow-up coronary angiogram demonstrated significant difference in the percent of diameter in the stenosed coronary between two groups ($Group\;1:\;40.3{\%},\;Group\;2:\;25.5{\%}$). Flow-velocity wave obtained from in vivo intracoronary Doppler ultrasound data is used for the boundary condition for the computer simulation. Spatial and temporal variations of flow velocity vector and recirculation area are drawn throughout the selected segment of coronary models. The WSS of pre- and post-intracoronary stenting are calculated from three-dimensional computer simulation. Then negative shear stresses area on 3D simulation we noted on the inner wall of the post-stenotic area before stenting. The negative WSS is disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2. The present study suggest that hemodynamic forces exerted by pulsatile coronary circulation termed WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. The local recirculation area which has low or negative WSS, might lead to progression of atherosclerosis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.753-758
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• 2003

The purpose of the present study was to establish the mechanism of the generation of atherosclerosis by analyzing the hemodynamic variables in the coronary artery where atherosclerosis occurs frequently. From the previous results, the stenosis phenomena due to atherosclerosis were related to not only biochemical reaction between blood and blood vessel but also the hemodynamic factors like flow separation and oscillatory wall shear stress. The present study aimed to investigate the causes of the generation and progression of atherosclerosis in the coronary artery. This study also aimed to develop the softwares which generate automatically three dimensional vascular models obtained by the angiogram images and the computer vision techniques. In the present study, the flow patterns for full three-dimensional hemodynamic characteristics were analyzed. To understand the three-dimensional hemodynamic characteristics, the wall shear stress distributions and secondary flows were investigated quantitatively.

• 대한의용생체공학회:의공학회지
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• 제36권6호
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• pp.264-270
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• 2015

A mock circulatory loop system has been developed to construct a simulator for trainees in cardiopulmonary bypass systems or to simulate a test environment for cardiac-assist devices. This paper proposes a computerized mock circulatory loop system whose node is modularized by using a servo control flow regulator to simulate dynamic change of the hemodynamic status. To observe the effect of time-varying resistance, one with hemodynamic properties, the proposed system replicates the planned cross-sectional areas of the outlet of a ventricular assist device in terms of voltage input of a servo valve. The experiment is performed (1) for steady-input commands of selected area sizes and (2) for dynamic commands such as monotonous increase and decrease, and oscillatory functions of the voltage input, and a computer program based on LabVIEW (National Instruments, Austin, USA) processes every measured data and control command to the servo valve. The results show that the pressure and flow at the target points with respect to time-varying resistance match intuitive estimation: the pressure at the outlet and the pressure drop between both sides of the valve increased and the flow at the outlet decreased for increased resistance.

• 대한수의학회지
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• 제35권3호
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• pp.595-601
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• 1995

Hemodynamic values were assessed in the cows diseased with mastitis. Hemodynamic testes were performed for white blood cell(WBC), red blood cell(RBC), packed cell volume(PCV), hemoglobin concentration, monocyte, eosinophil, neutrophil, lymphocyte, prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, platelet concentrations, antithrombin-III and plasminogen activities. Significant alterations were observed in the mean values of most analytes. The numbers of monocytes, eosinophil, and neutrophil, and prothrombin time were increased while the number of lymphocyte, activated partial thromboplastin time, thrombin time, fibrinogen concentration, plasminogen activity and platelet concentration were decreased. The number of RBC, PCV, hemoglobin and antithrombin-III activity were unchanged compared with normal mean values. These data indicated that activation of hemodynamic mechanisms was initiated either directly by the endotoxin-releasing or indirectly by the inflammatory mediators released by response to etiologic agents. We suspected that the changes of hemodynamic values in the cows diseased with mastitis were very similar to those of experimental endotoxin-induced mastitis.

• Journal of Korean Neurosurgical Society
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• 제37권3호
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• pp.207-212
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• 2005

Objective: Classically, single photon emission tomography is known to be the reference standard for evaluating the hemodynamic status of patients with moyamoya disease. Recently, T2-weighted perfusion magnetic resonance(MR) imaging has been found to be effective in estimating cerebral hemodynamics in moyamoya disease. We aim to assess the utility of perfusion-weighted MR imaging for evaluating hemodynamic status of moyamoya disease. Methods: The subjects were fourteen moyamoya patients(mean age: 7.21 yrs) who were admitted at our hospital between Sep. 2001 to Sep 2003. Four normal children were used for control group. Perfusion MR imaging was performed before any treatment by using a T2-weighted contrast material-enhanced technique. Relative cerebral blood volume(rCBV) and time to peak enhancement(TTP) maps were calculated. Relative ratios of rCBV and TTP in the anterior cerebral artery(ACA), middle cerebral artery(MCA) and basal ganglia were measured and compared with those of the posterior cerebral artery(PCA) in each cerebral hemispheres. Using this data, we analysed the hemodynamic aspect of pediatric moyamoya disease patients in regarding to the age, Suzuki stage, signal change in FLAIR MR imaging, and hemispheres inducing symptoms. Results: The mean rCBV ratio of ACA, MCA did not differ between normal children and moyamoya patients. However the significant TTP delay was observed at ACA, MCA territories (mean = 2.3071 sec, 1.2089 see, respectively, p < 0.0001). As the Suzuki stage of patients is advanced, rCBV ratio is decreased and TTP differences increased. Conclusion: Perfusion MR can be applied for evaluating preoperative cerebral hemodynamic status of moyamoya patients. Furthermore, perfusion MR imaging can be used for determine which hemisphere should be treated, first.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.6-9
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• 2008

Analyzing the characteristics of blood flow in the blood vessels is very important to diagnose the circulatory diseases. In order to investigate the hemodynamic characteristics in vivo, the measurements of blood flows inside the extraembryonic arterial and venous blood vessels of chicken embryos were carried out using an in vivo micro-PIV technique. The circulatory diseases are closely related with the formation of abnormal hemodynamic shear stress regions, thereby it is important to get blood velocity and vessel's morphological information according to the vessel configuration and the flow conditions. In this study, the flow images of RBCs in blood vessels were obtained using a high-speed CMOS camera with a spatial resolution of approximately 14.6${\mu}$m${\times}$14.6${\mu}$m in the whole circulation network of blood vessels. The blood flows in the veins and arteries show steady laminar and unsteady pulsatile flow characteristics, respectively. The mean blood flows merged (in veins) and bifurcated (in arteries) smoothly into the main blood vessel and branches, respectively, without any flow separation or secondary flow which accompanying large variation of shear stress. Vorticity was high in the inner regions for both types of vessels, where the radius of curvature varied greatly. The instantaneous flows in the arterial blood vessels showed noticeable pulsatility due to the heart beat, and the main features of the velocity waveforms, including pulsatile shape, retrograde flow, mean velocity, maximum velocity and pulsatile frequency, were significantly dependent on the pulsatile condition which dominates the arterial blood flow. In near future, these in vivo experimental results of blood flow measured in various extraembryonic blood vessels would be very useful to understand the hemodynamic characteristics of human blood flows and various blood flow researches for clinically useful hemodynamic discoveries as well.