• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.215-220
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• 1996

Impact force and strains induced by impact between the occluder and the struts have been measured with force sensor and strain gages. The maximum reaction force was about 25N, and the calculated impact force on the root of the struts amount about 9-17W. Impact force on the inlet strut is greater than that of the outlet strut, but the strain on the outlet strut is much higher than that of the inlet strut. These values might cause severe damage on the valve in the critical cases. The results of this study may be extended for the analysis of the endurance limit and optimal design of the struts and occluder.

• Journal of Chest Surgery
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• v.12 no.4
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• pp.383-394
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• 1979

Treatment of valvular heart disease with valve replacement has been one of the most popular procedures in cardiac surgery recently. Although, first effort was directed toward the prosthetic valve, it soon became popular that bioprosthesis, the valvular xenograft, was prefered in the majority cases. Valvular xenograft has some superiority to the artificial prosthetic valve in some points of thromboembolism and hemolytic anemia, and it also has some inferiority of durability, immunologic reaction and resistance to Infection. Tremendous efforts were made to cover the inferiority with several methods of collection, preservation, and valve mounting of the porcine valve or pericardium of the calf, and also with surgical technique of the valvular xenograft replacement. Auther has collected 320 porcine aortic valves immediately after slaughter, and aortic cusps were coapted with cotton balls in the Valsalva sinuses to protect valve deformity after immersion in the Hanks' solution, and oxidation, cross-linking and reduction procedures were completed after the proposal of Carpentier in 1972. Well preserved aortic valves were suture mounted in the hand-made tissue valve frame of 19, 21, and 23 mm J.d., and also in the prosthetic vascular segment of 19 mm Ld. with 4-0 nylon sutures after careful trimming of the aortic valves. Completed valves were evaluated with bacteriologic culture, pressure tolerance test with tolerane gauge, valve durability test in the saline glycerine mixed solution with tolerance test machine in the speed of 300 rpm, and again with pathologic changes to obtain following results: 1. Bacteriologic culture of the valve tissue in five different preservation method for two weeks revealed excellent and satisfactory result in view of sterilization including 0.65% glutaraldehyde preservation group for one week bacteriologic culture except one tissue with Citobacter freundii in 75% ethanol preserved group. 2. Pressure tolerance test was done with an apparatus composed of V-connected manometer and pressure applicator. Tolerable limit of pressure was recorded when central leaking jet of saline was observed. Average pressure tolerated in each group was 168 mmHg in glutaraldehyde, 128 mmHg in formaldehyde, 92 mmHg in Dakin's solution, 48 mmHg in ethylene oxide gas, and 26 mmHg in ethanol preserved group in relation to the control group of Ringer's 90 mmHg respectively. 3. Prolonged durability test was performed in the group of frame mounted xenograft tissue valve with 300 up-and-down motion tolerance test machine/min. There were no specific valve deformity or wearing in both 19, 21, and 23 mm valves at the end of 3 months (actually 15 months), and another 3 months durability test revealed minimal valve leakage during pressure tolerance test due to contraction deformity of the non-coronary cusp at the end of 6 months (actually 30 months) in the largest 23 mm group. 4. Histopathologic observation was focussed in three view points, endothelial cell lining, collagen and elastic fiber destructions in each preservation methods and long durable valvular tolerance test group. Endothel ial cell lining and collagen fiber were well preserved in the glutaraldehyde and formaldehyde treated group with minimal destruction of elastic fiber. In long durable tolerance test group revealed complete destruction of the endothelial cell lining with minimal destruction of the collagen and elastic fiber in 3 month and 6 month group in relation to the time and severity. In conclusion, porcine xenograft treated after the proposal of Carpentier in 1972 and preserved in the glutaraldehyde solution was the best method of collection, preservation and valve mounting. Pressure tolerance and valve motion tolerance test, also, revealed most satisfactory results in the glutaraldehyde preserved group.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1081-1086
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• 2009

This paper presents dynamic characteristics of pneumatic artificial muscles. Since the actuating performance of a pneumatic muscle is closely related to the input pressure of a pneumatic muscle, the air flow model on a valve orifice and an elastic bladder of the muscle is formulated to estimate precisely the pressure variance of pneumatic muscles during deflating and inflating process. Frequency response experiments are performed with an antagonistic system consisting of two pneumatic muscles and fast pneumatic control valves. Comparing with experimental results, the proposed model yielded good performance in estimating dynamic motions of the antagonistic system as well as the pressure variance of the pneumatic artificial muscles

• Journal of Biomedical Engineering Research
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• v.13 no.3
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• pp.225-234
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• 1992

In order to use a low cost polymer valve in our total artificial heart and ventricular assist device, we have developed a slit-type bileaflet polymer valve[BPV 1. The aim of this study is to determine the hydrodynamic effectiveness of the newly-designed BPV and its feasibility for temporary use in the blood pumps. For hydrodynamic comparison, we investigated in-vitro the pressure drop across the valve, the leakage volume, the flow rate and the flow pattern of the BPV, two mechanical valves and a trileaflet polymer valve. We employed the ventriculo-pulmonary bypassing method for in-vivo tests of the BPV's together vilh our electrohydraulic left venIn ricular assist device in mongrel dogs. The BPV showed adquate gydrodynamic performances and in the preliminary animal bests, there was no xvi dence of thrombus formation on the valve leaflets and around the struts. Detailed results obtained from the animal tests will be separately reported. This report involves the design criteria, fabrication and hydrodynamic charateristics of she BPV, and the basic merits and demerits of the valve are dis- cussed from the hydrodynamic point of view.

• Journal of Chest Surgery
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• v.37 no.3
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• pp.220-227
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• 2004

The number of patients with coronary artery disease and peripheral vascular disease are increasing, and the need of small diameter vessel is also increasing. We developed small diameter artificial vessel and experimented in vivo. We got allogenic valve from mongrel dogs, and removed all cells from the allogenic valve. Then, we seeded autologous bone marrow cells onto the decellularized scaffold. After implantation of artificial vessel into the canine carotid artery, we performed angiography regularly. In case of vessel occlusion or at 8 weeks after operation, we euthanized dogs, and retrieved the implanted artificial vessels. Control vessels were all occluded except one (which developed aneurysmal dilatation). But autologous cell seeded vascular graft were patent by 4 weeks in one, by 6 in one and by 8 weeks in two. Histologic examination of patent vessel revealed similar structure to native artery. Tissue-engineered vascular graft manufactured with decellularized allogenic matrix and autologous bone marrow cells showed that tissue engineered graft had similar structure to native artery.

• Journal of Chest Surgery
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• v.14 no.3
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• pp.247-253
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• 1981

A total and consecutive 46 patients have undergone cardiac valvular surgery including 8 open mitral commissurotomy and 38 mitral, aortic, mitral-aortic, mitral-tricuspid, tricuspid valve replacements using 46 artificial valves in a period between September 1976 and July 1981. They were 19 males and 27 females with the age ranging from 16 to 50 (mean 32.6) years. Out of 46 valves replaced, 6 were prosthetic valves and 40 were tissue valves, and 33 were replaced in mitral, 9 in aortic and 3 In tricuspid position. Isolated replacements were 33 mitral valves, 6 aortic valves and 1 tricuspid valve; double valve replacements were 6 mitral-aortic valves and 2 mitral-tricuspid valves. . Early mortality within 30 days after operation was noted in 4 cases; 3 after MVR and 1 after open mitral commissurotomy. Causes of death were thrombus obstruction of Beall-Surgitool, Cerebral air embolism, acute renal shut down due to low output syndrome, and left upper pUlmonary vein rupture after open mitral commissurotomy (early mortality 8.7%). 3 late deaths were noted during the follow-up period from 2 to 59 months; 1 due to cerebral hemorrhage from warfarin overdose 3 months, 1 due to miliary tuberculosis 9 months, and another 1 due to cardiac failure after open mitral commissurotomy 42 months postoperatively. Total survival rate 59 months after valvular surgery was 84.8%; there were no early and late death in the group of AVR, TVR and double valve replacements. Preoperative NYHA Class III & IV were 35 cases (76%) out of total 46 cases, and 38 cases (94.8%) out of 39 survival cases were included In NYHA Class I & II during the follow-up period.

• Journal of Chest Surgery
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• v.27 no.4
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• pp.272-280
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• 1994

Total 400 St.Jude Medical Bileaflet Valves were implanted in 336 pts from January 1983 to June 1993; 64 were aortic, 205 were mitral, 64 were double valve and 3 were tricuspid position. The follow up period extended from 6 months to 10 years[mean 24.3 months]. Male to female ratio was 1:1.7. There were total 27 deaths[cardiac related 20, cardiac non-related 7]. Overall mortality was 2.9%/pt-yr. There were 10 early deaths[3.0%] and 10 late cardiac related deaths [3.0%]. Prosthetic valve related complications occurred in 19 patients[5.7%] and among them, seven died; four died of thromboembolic events, two died of anticoagulants therapy related hemorrhagic complications and one died of bacterial endocarditis. NYHA class improved significantly especially in aortic valve replacement and double valve replacement. In AVR cases, the mean NYHA was 2.8 preoperatively and 1.3 postoperatively. And in DVR cases, 3.3 preoperatively and 2.2 postoperatively. The decision to employ a particular prosthesis was made according to the anticipated or known complications of the valve. The St.Jude Medical Valve retains all the hazards of other mechanical valves, most notably, thromboembolism. But the hemodynamic performance of St.Jude Medical Valve compared most favorably with other substitute valves in many reports. 0ur experience didn`t show any differences compared other authors in terms of valve related complication. So we concluded St. Jude Medical Valve can be primarily considered in the selection of artificial valve except in the patients when the usage of anticoagulant therapy is contraindicated.

• Journal of Chest Surgery
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• v.34 no.9
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• pp.680-685
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• 2001

Background: Tricuspid valve replacement is very rarely performed procedure and its long-term result is not yet satisfactory. Moreover, it is not well known whether bioprosthesis or mechanical prosthesis is the best selection for artificial valve. We reviewed 72 cases of tricuspid valve replacements in 71 patients between January 1989 and December 1998, trying to analyze the overall results and risk factors for mortality and morbidity. Material and Method: Average age of the patients at the time of operation was 42$\pm$13 years(range 16 to 65 years) and the sex ratio of male versus female was 32/39. Primary diagnosis consisted of 50 cases of aquired valvular heart disease and 18 cases of congenital heart disease, such as Ebstein’s anomaly. 4 cases had isolated tricuspid valve regurgitation. Implanted valves were 69 mechanical prosthesis and 3 bioprosthesis. Concomitant mitral or aortic valve replacements were performed in 50 cases. One patient received concomittant pulmonary valve replacement. Result: There were 7(9.72%) operative deaths and 7(13.0%) late deaths. Actuarial survival at 10 years was 59.2$\pm$7.2%. Prosthetic tricuspid valve thrombosis occurred 11 times in 5 patients. Reoperation for prosthetic tricuspid valve failure was performed in 1 patient. In this case, examination of the explanted prostheses showed that the tricuspid stenosis was the result of valve thrombosis. Among the 47 survivors, 46 patients(98%) were in functional class I or II. Conclusion: In our ten-year experience of tricuspid valve replacement, mortality and morbidity were satisfactory. Mechanical prosthesis in tricuspid position showed comparable clinical results as bioprosthesis.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.1-15
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• 1997

Titanium oxide films were prepared by ion beam enhanced deposition where the films were synthesized by deposition titianium atoms and simultaneously bombarding with xenon ion beam at an energy of 40 keV in an $O_2$ environ,ent. Structure and composition of titanium oxide films were investigated by X-ray Doffractopm (XRD) Ritjerfprd Backscattering Spectroscopy (RBS) and X-ray Diffraction(XRD) Rutherford Backscattering Spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) The results show that thestructure of the prepared films exhibit a rutile phase structure wit high(200) orientation and the O/Ti ratio of the titanium oxide films was about 2:1 XPS anlysis shows that $Ti^{2+},Ti^{3+}\;and\;Ti^{4+}$ chemical states exist on the titanium oxide films. the blood compatibility of the titanium oxide films was studied by measurements of blood clotting time and platelet adhesion. The results show that the anticoagulation property of titanium oxide films improved significantly and better than that of LTI-carbon which was widely used to fabricate artificial heart valve.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.1
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• pp.69-77
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• 2011

A peristaltic micropump with lightweight piezo-composite actuator (LIPCA) membrane valves is presented. The micropump contained three cylinder chambers that were connected by microchannels and two active membrane valves. A circular miniature LIPCA was developed and manufactured to be used as actuating diaphragms. The LIPCA diaphragm acted as an active membrane valve that alternate between open and closed positions at the inlet and outlet in order to produce high pumping pressure. In this LIPCA, a lead zirconium titanate ceramic with a thickness of 0.1 mm was used as an active layer. The results confirmed that the actuator produced a large out-of-plane deflection. During the design process, a coupled field analysis was conducted in order to predict the actuating behavior of the LIPCA diaphragm; the behavior of the actuator was investigated from both a theoretical and experimental perspective. The active membrane valve concept was introduced as a means for increasing pumping pressure, and microelectromechanical system techniques were used to fabricate the peristaltic micropump. The pumping performance was analyzed experimentally in terms of the flow rate, pumping pressure and power consumption.