• Journal of Chest Surgery
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• v.37 no.3
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• pp.245-251
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• 2004

Hemostatic function is regarded to be preserved after an off-pump coronary artery bypass grafting (CABG), compared to conventional CABG, and the preserved hemostatic function may increase thrombotic occlusion of the graft. We studied the changes of hemostatic variables in patients undergoing off-pump CABG, and compared to those of on-pump CABG. We studied the changes of coagulation function in 11 patients who underwent off-pump CABG (group I), and compared them with those of 11 patients who underwent on-pump CABG and Dor procedure (group II). Coagulation status was evaluated by thromboelastography and blood coagulation test preoperatively, postoperative 1$^{st}$ day, 2$^{nd}$ day, 3$^{rd}$ day, and 5$^{th}$ day, respectively. Among the variables measured by thromboelastography (such as r time, k time, $\alpha$ angle, and MA value) and blood coagulation test (such as factor Ⅶ, protein S, protein C, antithrombin III, activated protein C resistance test, plasminogen, D-dimer, prothrombin time, activated partial thromboplastin time, platelet count, hemoglobin, and fibrinogen), there were significant differences in the MA value, $\alpha$ angle, and platelet counts between the two groups. MA values were 140$\pm$72% and 153$\pm$98% in group I, and 87$\pm$27% and 78$\pm$28% in group II, at postoperative 3$^{rd}$ and 5$^{th}$ days, respectively (p<0.05). $\alpha$ angle was 122$\pm$92% in group I and 69$\pm$23% in group II at postoperative 3$^{rd}$ day (p=0.09). Platelet count was 63$\pm$55% in group I and 33$\pm$13% in group II at postoperative 3$^{rd}$ day (p<0.05). Patients who underwent off-pump CABG showed increased coagulability during postoperative periods, compared to those who underwent on-pump CABG. Our data suggest that aggressive perioperative anticoagulation therapy is warranted in patients undergoing off-pump CABG. CABG.

• Journal of Power System Engineering
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• v.11 no.2
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• pp.38-43
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• 2007

전자기적으로 지지되는 임펠러를 가진 원심 혈액 펌프는 기존의 심장 펌프에 비해 많은 장점을 가지고 있지만, BVAD의 틈새에서 발생하는 유체 동역학적인 문제는 여전히 규명이 되지 않은 상태이다. 본 연구에서는 BVAD의 틈새에서 발생하는 혈액외상(blood trauma)의 예측에 대한 연구에 중점을 두고 있다. 일반적으로 원심 혈액 펌프의 설계를 위해 전자기적으로 지지되는 원심 혈액 펌프의 디스크 틈새에서 발생하는 혈액의 손상을 평가하는 방법으로 CFD를 이용한 방법이 널리 이용되고 있다. 따라서, 본 연구에서는 초기 원심 혈액 펌프의 설계 단계에서 펌프의 특성을 평가하기 위하여, 축 방향 틈새의 영향과 회전수 변화에 따른 누수경로의 전단 응력의 크기 평가를 CFD를 사용하여 해석하여 보았다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.13-18
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• 2001

The ECMO system, including umbilical cord and membrane type oxygenator was connected with extracorporeal circulation unit, was applied to the fetus growth model of goat. The maximum survival time of goat fetus was 48 hours. Average blood rate for the extracorporeal circulation was $223{\pm}15.2 ml/min.$ The survival time of fetus was deeply related to body temperature, blood circulation and water temperature, anesthetized time, and fetus weights. Extern variables that are composed of anesthetized time, fetus weights, change of hemoglobin, circuit pressure, related to the survival time for fetus corrected the problem of previous ECMO model that is controlled by roller pump. It is directly delivered to heart on load. Applying the results from new ECMO model, further research will provide to the system of ECMO for human.

• Journal of Biomedical Engineering Research
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• v.28 no.3
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• pp.387-391
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• 2007

An oxygenator is a very important artificial organ and widely used for patients with lung failure or during open heart surgery. Although an oxygenator has been widely studied worldwide to enhance its efficiency, studies on oxygenators, in particular when using a pulsatile blood flow, are domestically limited. Therefore, a new oxygenator was developed in the lab and animal experimental results are described in the paper. The oxygenator is composed of polycarbonate housing and polypropylene hollow fibers. It has a total length of 400 mm and a surface area of $1.7 m^2$. The animal experiment lasted for 4 hours. The blood flow rate was set to 2 L/min and a pulsatile blood pump, T-PLS (Twin-Pulse Life Support), was used. Samples were drawn at the oxygenator's inlet and outlet. The total hemoglobin (Hb), saturation oxygen ($sO_2$), and partial oxygen pressure ($pO_2$), partial $CO_2$ pressure ($pCO_2$), and plasma bicarbonate ion concentration ($HCO_3^-$) were measured. The oxygen and carbon dioxide transfer rates were also calculated based on the experimental data in order to estimate the oxygenator's gas transfer efficiency. The oxygen and carbon dioxide transfer rates were $16.4{\pm}1.58$ and $165.7{\pm}10.96 mL/min$, respectively. The results showed a higher carbon dioxide transfer rate was achieved with the oxygenator. Also, the mean inlet and outlet blood pressures were 162.79 and 137.92 mmHg, respectively. The oxygenator has a low pressure drop between its inlet and outlet. The aim of own preliminary study was to make a new oxygenator and review its performance when applying a pulsatile blood pump thus, confirming the possibility of a new oxygenator suitable for pulsatile flow.

• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.65-70
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• 2004

In this paper, we described 23 cases of animal experiment with our pneumatic ventricular assist device and new durability-improvement method. The blood pump consists of blood housing, and back plate made by the injection molding of isoplast, and the diaphragm fabricated by dipping of polyurethane solution onto the aluminum mold. Its volume was 75 $m\ell$ and in-vitro test showed that maximum output was 4.5 $\ell$/min at the 100 mmHg. The adult female sheep with weight of 50 ＋ 10 kg were employed for tile in-vivo experiments and the mean blood flow was sustained at 3.0 1/min. 4 animals survived more than 15 days and the longest survival time was 28 days. In the prior 10 cases, the major causes of death were the tearing of diaphragm at the diaphragm to blood housing junction. By the new mesh and alumina ball milling methods, the durability was enhanced, and its qualitative and quantitative improvement was proved via the in-vivo and in-vitro methods. Animal experiments demonstrated that all the physiologic parameters a ere maintained within the permissible ranges and no thrombus formation was observed through the visual and blood test. The in-vivo experiments demonstrated our pneumatic ventricular assist device to he one month's bridge to transplantation device.

• Journal of Biomedical Engineering Research
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• v.19 no.1
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• pp.33-38
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• 1998

The intracardiac axial flow pump has been developed This device has several advantages: it fits well anatomically, its blood-contacting surface is small, and it is implanted as easily as an artificial heart valve replacement. The axial flow pump consists of an impeller and a motor, both of which are encased in a housing. Two types of impeller with 4 vanes and 6 vanes are used. Sealing of the motor shaft is achieved by means of a ferrofluidic seal. A flow of 5$\ell$/min was obtained at a differential pressure of 100mmHg with a motor speed of 7091rpm with the 4-vane impeller and 6402rpm with the 6-vane impeller. Sealing was kept against a pressure of 150mmHg at 7000rpm with the 4-vane impeller and 6402rpm with the 6-vane impeller. Sealing was kept against a pressure of 150mmHg at 7000rpm over 24 hours. The index of hemolysis was 0.056 with the 4-vane impeller and 0.214 with the 6-vane impeller. The intracardiac axial flow pump is a very promising circulatory support.

• Biomedical Science Letters
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• v.17 no.4
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• pp.337-345
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• 2011

It is well recognized that conventional coronary artery bypass grafting (ONCAB) often leads to major organ dysfunction including renal injury. Diabetes mellitus is a major cause of nephropathy and poor clinical outcomes. The aim of this retrospective study was to evaluate the occurrence of adverse outcomes including renal impairment between diabetic (n=75, DM group) and non-diabetic patients (n=72, Non-DM group) underwent off-pump coronary artery bypass grafting surgery (OPCAB). Fasting glucose, hemoglobin A1c, fructosamine, fibrinogen and serum osmolality levels in the DM group were higher than those of the Non-DM group at pre-operative (Pre-OP) period ($P$ <0.05). History of hypertension and renal impairment in the DM group was higher than that of the Non-DM group ($P$ <0.05). Potassium ($K^+$), blood urea nitrogen and creatinine levels were higher, whereas sodium ($Na^+$) and glomerular filtration rate (GFR) levels were lower in the DM group than the Non-DM group at peri-operative period ($P$ <0.05). Fasting glucose levels at Pre-OP period had positive correlations with blood urea nitrogen and creatinine levels at peri-operative period, but negative correlations with GFR levels at peri-operative period in the DM group ($P$ <0.05). Incidences of renal impairment, diuretic therapy or continuous renal replacement therapy and fever in the DM group were higher than those of the Non-DM group at post-operative period ($P$ <0.05). These results suggest that blood glucose level should be tightly controlled at peri-operative period to avoid renal dysfunction in diabetic patients.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.11
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• pp.521-527
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• 2002

The Hemodialysis system is the device for the patients who have suffered from end stage renal failure as the kidney which removes the waste products in a human body. The existing hemodialysis is based on a 8-bit micro-controller and it is not a touch-screen type but a manual type. This paper is focused on hemodialysis system based on high control and expension embedded system. The whole system consists of main control unit and sub control unit(dialysis control unit, blood control unit, monitoring control unit, networking unit). The dialysis control unit, blood control unit, monitoring control unit are processed by 3 microcontrollers and network unit is for monitoring a renal failure patient's condition. For the evaluation of the system performance, the saline was pured into blood unit and then water removal rate, conductivity and temperature of hemodialysis liquid were measured 10 times in an each state suing the UF pump in the fluid unit varing the quantity of saline to 1000cc, 2000cc, 3000cc and 4000cc. As a result, the rates of water removal are 98.6% in condition of 000cc saline, 96.9% in 2000cc, 98.9% in 3000cc and 98.3% in 4000cc. The conductivities of hemodialysis liquid are 99.6% in the first to third condition and 99.7% in the forth condition. The temperatures of hemodialysis liquid are 99.8% in the first to third condition and 99.6% in th forth condition.

• Journal of Chest Surgery
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• v.45 no.5
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• pp.301-307
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• 2012

Background: Perioperative transfusion of red blood cell (RBC) may cause adverse effects. Bloodless-cardiac surgery has been spotlighted to avoid those problems. Off pump coronary artery bypass (OPCAB) surgery can decrease the transfusion. However, the risk factors of transfusions in OPCAB have not been investigated properly. Materials and Methods: One hundred and thirteen patients (male:female=35:78, mean age=$66.7{\pm}9.9$ years) who received isolated OPCAB were retrospectively analyzed from March 2006 to September 2007. The threshold of RBC transfusion was 28.0% of hematocrit. Bilateral internal thoracic arteries graft were used for 99 patients (87.6%). One hundred and three (91.1%) and 35 patients (31.5%) took aspirin and clopidogrel just before surgery. Results: Sixty-five patients (47.5%) received the RBC transfusion (mean $2.2{\pm}3.2$ units). Mortality and major complications were not different between transfusion and no-transfusion group. But, ventilator support time, intensive care unit stay and hospitalization period had been reduced in no-transfusion group (p<0.05). In multivariate analysis, patients risk factors for RBC transfusion were preoperative low hematocrit (<37.5%) and clopidogrel medication. Surgical risk factors were longer graft harvesting time (<75 minutes) and total operation time (<5.5 hours, p <0.05). Conclusion: We performed the transfusion according to transfusion guideline; over 40% cases could conduct the OPCAB without transfusion. There were no differences in major clinical results between transfusion and non-transfusion group. In addition, when used together with accurate understanding of transfusion risk factors, it is expected to increase the proportion of patients that do not undergo transfusions.

• Proceedings of the KOSOMBE Conference
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• v.1990 no.05
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• pp.1-6
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• 1990

A new version of moving actuator electromechanical total artificial heart was designed to improve total efficiency, durability, and fitting inside thoracic cavity. As compared with our present type of the rolling cylinder actuator, this new model has a pendulum-type actuator with reciprocating motion around the fixed circular path, connected through the gear mechanisms to the motor. By using this mechanism, the efficiency and durability could be improved by replacing sliding mechanism with rolling contact elements. Also, the height of the pump could be decreased from 9cm to 7cm with static stroke volume 65cc. With these improvements, we have implanted this new pump in human size animal (less than 70Kg weight).