摘 要
本研究所設計之左心室輔助器，乃根據文獻外型與尺寸設計一相似原始模型(外徑為35mm、長度80mm)，接著以數值模擬進行三維紊流流場的數值分析，探討其內部流場模式、壓力、剪應力大小等與破壞血球之可能性。數值結果顯示在8,000rpm下，其流量為8.07L/min可滿足基本需求，但其最大剪應力遠超過產生溶血反應之需求。為解決此項缺點，且在方便植入人體之考量下，本文縮小整體尺寸並搭配磁浮馬達為動力來源，重新設計一小尺寸的左心室輔助器(外徑20mm、長度60mm)，並進行一系列參數分析探討，所探討參數包含外徑變化、前噴嘴與後擴散器長度、導流葉片數與轉速變化。數值分析結果顯示，在固定內徑(9mm)下外徑大小由16mm到35mm的變化，其流量由0.56L/min增至9.78L/min，且隨外徑增加而增加；在前噴嘴與後擴散器長度10mm減為5mm時，流量也隨之增加。然而在不同導流葉片數(7片與9片)下，流量不受太大影響；轉速在2,000rpm與8,000rpm時所受最大剪應力分別為160 與2410 ，而流量分別為3.06L/min與8.07L/min，流量隨轉速而降低。上述參數之組合經數值計算得到一最佳化設計，其外徑為20mm、導流葉片數7片、噴嘴、擴散器長度為5mm，並在3,000rpm時受到最大剪應力為903.75 ，低於文獻中提及產生溶血之臨界剪應力，足以避免引發溶血反應與血栓，且流量為4.73L/min滿足基本需求，本研究之結論可作為日後進一步改善左心室輔助器之設計參考。

Abstract
This work intends to study a left ventricular assist device (LVAD) with the aids of pump theory and CFD code Star-CD. At first, a LVAD with 35-mm-diameter and 80mm-length, which is similar to the size listed in literature, is constructed based on the model of axial-flow pump with inlet and outlet guide vanes. Next, the numerical analysis is applied to simulate the turbulent flow field to explore the possibility of the correlations among the flow patterns, the pressure distribution, the shear stress, and the blood’s destruction. The result shows that this model operating at 8,000 rpm generates 8.07 l/min flow rate that could meet with the basic demand; however, the maximum shear stress existed was far beyond the requirement for preventing heterolysis reaction and thrombi. In order to solve this problem and consider the convenience of planting the device into the human’s body, this research shortened its size and redesigned a small LVAD that is in 20-mm diameter and 60-mm length with the magnetic float motor as the power source. In addition, a series of numerical analysis was conducted to investigate the LVAD characteristics influenced by important parameters that include the outside diameter, the length of inlet nozzle and outlet diffuser, the number of guiding blades, and the rotational speed. When the inner diameter was fixed in 9 mm, the analyses indicated that the flow rate enlarged from 0.56 l/min to 9.78 l/min for an increasing outside diameter from 16mm to 35mm. In addition, the flow rate increases when the length of inlet nozzle and outlet diffuser was reduced from 10 mm to 5 mm. However, the flow rate would not change even though the guide vane numbers were different. With regard to the variation in pump speed, the volume rate would increase directly with the speed as predicted by the pump law. Notice that, the maximum shear stress was increasing significantly from 160 to 2410 for the rotational speed ranging from 2000 to 8000 rpms. In conclusion, an optimal LVAD operating at 3,000 rpm could be obtained successfully to deliver a 4.73 l/min flowrate while the maximum shear stress was only 903.8 . Clearly, the requirements on flowrate and shear stress were satisfied by this LVAD model featured with seven guiding blades, a 20-mm-diameter, and a 5-mm length of the inlet nozzle and outlet diffuser.

參 考 文 獻
[1]林佑穗、袁宗凡所著, “新編蓋統醫用生理學”, 2000。
[2]賴亮全、林則彬、林富美合譯, Guyton, A. C. and Hall, J. E. 編著，“蓋統生理學:生理及疾病機轉”, 1998。
[3]洪敏元, “當代生理學”, 2002。
[4]Austin, J. W. and Harner, D. L., “The heart-lung machine and related technologies of open heart surgery,” 1st ed., Phoenix Medical Co., 1986.
[5]DeVires, W. C. and Joyce, L. D., “The artificial heart,” Clinical Symposia CIBA 35, pp. 5-32, 1983.
[6]張燕、鄭國琪、賴曉亭、游堂振、郭樹民、翁仁崇、李秉純、鄭伯智、陳經倫, “人工心臟,” 臨床醫學, 第26卷第6期, pp. 442-445, 1988年12月。
[7]Olsen, D. B., “Artificial organs of the future,” ASAIO Journal, pp.134-138, 1992.
[8]Johnson, K. E., Liska, M. B., Joyce, L. L., and Emery, R. W., “Use of total artificial hearts: Summary of world experience 1969-1991,” ASAIO Journal, Vol. 38, pp. 486-492, 1992.
[9]Affeld, K., “A new electrohydraulic energy converter for a left ventricular assist device,” Artificial Organ, Vol. 18, pp. 479-483, 1994.
[10]Rosarius, N., Sie, B., Reul, H., and Rau, G., “Concept realization and first in vitro testing of an intraarterial mincraxial blood pump with an integrated drive unit,” Artificial Organ, Vol. 18, pp. 512-516, 1994.
[11]Schima, H., Wieselthaler, T. G., Schmidt, C., Muller, M. R., Siegl, H., Losert, U., and Wolner, E., “The Vienna implantable centrifugal blood pump ,” Artificial Organ, Vol. 18, pp. 500-505, 1994.
[12]Wieselthaler, G. M., Schima, H., Hiesmayr, M., Pacher, R., Laufer, G., Noon, G. P., DeBakey, M., and Wolner, E., “First clinical experience with the DeBakey VAD continuous-axial-flow pump for bridge to transplantation,” Circulation , Vol. 101, pp. 356-359, 2000.
[13]Qian, K. X., “Low hemolysis pulsatile impeller pump： Design concepts and experimental results,” J. Biomed. Eng., Vol. 11, pp. 478-481, 1989.
[14]Qian, K. X., “Pulsatile impeller heart：A viable alternative to a problematic diaphragm heart,” Med. Eng. Phys., Vol. 18, pp. 57-66，1996.
[15]Didisheim, P., “Current concepts of thrombosis and infection in artificial organs,” ASAIO, pp. 229-237, 1993.
[16]Chiang, B. Y., “Thrombus with infection in total artificial heart animals,” Artificial Organs, Vol. 16, pp. 371-376, 1992.
[17]Schima, H. and Wieselthaler, G., “Mechanically induced blood trauma: Are the relevant questions already solved, or is it still an important field to be investigate?,” Artificial Organs, Vol. 41, pp. 584-587, 1995.
[18]Akutsu, T., “Total Replacement and Partial Support,” Artificial Heart, Tokyo: Igaku Shoin Ltd., 1975.
[19]Glover, C. J., McIntire, L. V., Leverett, L. B., Hellums, J. D., Brown, C. H., and Natelson, E. A., “Effect of shear stress on colt structure formation,” Trans Am Soc Artificial International Organs, Vol. 20, pp. 463-468, 1974.
[20]Hardwick, R. A., Hellums, J. D., Peterson, D. M., and Olson, J., “Effects of PGI and di-butry1 cyclis-AMP on platelets exposed to shear stress,” Trans Am Soc Artificial International Organs, Vol. 27, pp. 192-197, 1981.
[21]Johnston, G. G., Marzc, U., and Bernstein, E. F., “Effects of surface injury and shear stress on platelet aggregation and serotonin release,” Trans Am Soc Artificial International Organs, Vol. 21, pp. 413-421, 1975.
[22]Zumbro, G. L., Shearer, G., Fishback, M. E., and Galloway, R. F., “A prospective evaluation of the pulsatile assist device,” Ann Thorac Surg, Vol. 28, pp. 269-272, 1978.
[23]Levinson M. M., Smith R.G., Cork R.C., “Thromboembolic complications of the Jarvik-7 total artificial heart,” Artificial Organs, Vol. 10, pp. 236-244, 1986.
[24]Quaal, S., “The artificial heart,” Heart Lung, Vol. 14, pp. 317-327, 1985.
[25]Smith R. G., Levinson, M., and Callo, J., “Clinical problems facing recipients of total artificial hearts as bridge to cardic transplantation : results in two recent patients,” Artificial Organs, 1986.
[26]Taylor, K. D., Gaykowski, R., Keate, K. S., Winters, S., Price, R. R., and Topaz, S. F., “Explant analysis of thirty-three bridge to transplant J7 total artificial heart devices,” Trans. Am. Soc. Arti. Intern. Organs, Vol. 33, pp. 738-743, 1987.
[27]Lin J.Y., Hsu C.H., Cheng K.T., Tung C.S., and Lee Y.D., “Modeling and Analysis for the Electro-Hydraulic Pump of the Phoenix-7 Total Artificial Heart,” Show-Chwan Med. J., Vol.1, n.3, pp.141-147, 1999.
[28]Rizzoni, “Principle and Application of Electrical Engineering”, 4th ed., McGraw Hill, 2003.
[29]Mohrman, D. E. and Heller, L. J., : Cardiovasular Physiology.
[30]朱樹勳、錢坤喜, “人工心臟在台大的發展”, 醫學工程, 第6卷第4期，pp.124-128，1984
[31]Hunt S.A., and Frazier O.H., “Mechanical circulatory support and cardiac transplantation,” Circulation, Vol.97, pp.2079-2090, 1998
[32]Lena, Arzamanian, “About hemolysis,” Tech Talk, Vol. 2, No.2, 2003.
[33]Eck, B., “Fan”, Pergamon Press, N.Y., 1975
[34]Daniel, J. G. and Mehmet, C. Oz, “Cardiac assist devices,” Futura Publishing Company, Inc, 2000.
[35]Qolam, Reza and Mahrban, Moqadam, “Shear stress related blood damage in some cardiovascular devices with regard to laminar Couette flow,” University of Ghent, Artificial Organs, 2004
[36]蘇宗寶, “離心式泵”, 1986。
[37]Shames, Irving H., “Mechanics of fluids,” 3rd ed., McGraw Hill, 1992.
[38]樓迎統、陳君祝、黃榮棋、王錫五合著, 實用生理學, 2000。
[39]Croughan, M. S., Hamel, J. F. and Wang, D. C., “Hydrodynamic effects on animal cells grown in microcarrier cultures,” Biotechnology and Bioengineering, Vol. 29, pp. 130-141, 1987.
[40]Kunas, K. T. and Papoutsakis, E. T., “Damage mechanisms of suspended animal cells in agitated bioreactors with and without bubble entrainment,” Biotechnology and Bioengineering, Vol. 36, pp. 476-483, 1990.
[41]Kawase, Y. and Moo, Y. M., “Mathematical models for design of bioreactors: applications of Kolmogoroff’s theory of isotropic turbulence,” The Chemical Engineering Journal, Vol. 43, pp. 1319-1341, 1990.
[42]Papoutsakis, E. T., “Fluid mechanical damage of animal cells in bioreactors,” TIBTECH, Vol. 9, pp. 427-437, 1991.
[43]Lakhotia, S. and Papoutsakis, E. T., “Agitation induced cell injury in microcarrier cultures. Protective effect of viscosity is agitation intensity dependent: experiments and modeling,” Biotechnology and Bioengineering, Vol. 39, pp. 95-107, 1992.
[44]Spaet, T. H., Gaynor, E., and Stemerman, M. B., “Thrombosis atherosclerosis and endothelim,” Journal of American Heart, Vol. 87, pp. 661-668, 1974.
[45]Baldwin, J. T., Deutsch, S., Geselowitz, D. B. and Tarbell J. M., “Estimation of Reynolds stress fields within the penn state left ventricular assist device,” ASAIO Transactions, Vol. 36, pp. 274-278, 1990.
[46]Sturm, C., Li, W., Woodard, J. C. and Hwang, H. C., “Fluid mechanics of left ventricular assist system outflow housings,” ASAIO Transactions, Vol. 38, pp. 225-227, 1992.
[47]Brucker, C. H., “Dual-camera DPIV for flow studies past artificial heart valves,” Experiment in Fluids, Vol. 17, pp. 27-47, 1997.
[48]Hung, T. C., Hochmuth, R. M., Joist, J. H. and Sutera, S. P., “Shear- induced aggregations and lysis of platelets,” Trans. American Society of Artificial Internal Organs, Vol. 22, pp. 285-290, 1976.
[49]Smith, R., Blick, E., Coalson, J., and Stein, P., “Thrombus production by turbulence,” Journal of Applied Physiology, Vol. 32, pp. 261-264, 1972.
[50]Stein, P. D. and Sabbah, M. N., “Measured turbulence and its effect on thrombus formation,” Circulation Research, Vol. 35, pp. 608-614, 1974.
[51]Goldsmith, H. L. and Mason, S. G., "The flow of suspensions through tubes. I. single spheres, rods, and discs," J. Colloid Sci., Vol. 17, pp. 448-476, 1972.
[52]Karino, T. and Goldsmith, H. L., "Aggregation of human platelets in an annular vortex distal to a tubular expansion," Microvasc. Res., Vol. 17, pp.217-237, 1979.
[53]Thibault, L. E. and Fry, D. L., “Modulation of evans blue dye uptake in a canine aortic tissue preparation by hydrodynamically induced wall shear stress,” Advances in Bioengineering, pp. 267-270, 1980.
[54]Hellums, J. D. and Brown, C. H., “Blood cell damage by mechanical forces,” Univ. Park Press, Baltimore, MD, pp. 799-823, 1977.
[55]Tillman, W., Reul, H., Herold, M., Bruss, K. H. and Von, J., ”In vitro walls shear measurements at aortic valve prosthess,” J. Biomechanics, Vol. 17, pp. 263-279, 1984.
[56]Kameneva, Marina V., Antaki, James F., Borovetz, Harvey S., Griffith, Bartley P., Butler, Kenneth C., Yeleswarapu, Krishna K., Watach, Mary J., and Kormos, Robert L., “Mechanisms of red blood cell trauma in assisted circulation: rheologic similarities of red blood cell transformations due to natural aging and mechanical stress,” ASAIO Journal, Vol. 41, No. 3, pp. 457, 1995.
[57]Lamson, T. C., “Relative blood damage in the three phases of a　prosthetic heart valve flow cycle,” Ph.D. Thesis, The Pennsylvania State University, 1993.
[58]Baldwin, J. T., Deutsch, S., Geselowitz, D. B., and Tarbell, J. M., “LDA measurements of mean velocity and Reynolds stress fields within an artificial heart ventricle,” ASME Journal of Biomechanial Engineering, Vol. 116, pp. 190-200, 1994.
[59]Nichols, W. W. and Rourke, M. F., McDonald’s blood flow in arteries, 4th ed., Lea & Febiger, 1998.
[60]Wu, Z., “Cavitation in mechanical heart valve prostheses: an in-vitro study”, Ph. D. Thesis, University of Miami, 1996.
[61]Zapanta, C. M., “Correlation of prosthetic heart valve dynamics with cavitation：in vitro and in vivo studies”, Ph.D. Thesis, The Pennsylvania State University, 1997.
[62]Toshimasa, Tokuno, ”Cavitation inception of deceleration surfaces”, Ph.D. Thesis, University of Rice, 1978.
[63]Bluestein, D., Einav, S., Hwang, N., “A squeeze flow phenomenon at the closing of a bileaflet mechanical heart valve prosthesis,” J. Biomechanics, Vol. 27, pp. 1369-1378, 1994.
[64]Bachmann, C., Kini, V., Deutsch, S., Fontaine, A. A., and Tarbell, J. M., “Mechanisms of cavitation and the formation of stable bubbles on the Björk-Shiley Monostrut prosthetic heart valve,” The Journal of Heart Valve Disease, Vol. 11, pp. 105-113, 2002.
[65]STAR-CD, Version 3.15, Methodology, 2001.
[66]Patankar, S. V. and Spalding, D. B., “A calculation procedure for heat mass and momentum transfer in three-dimensional parabolic flows,” International Journal of Heat Mass Transfer, Vol. 15, pp. 1787-1806, 1972.
[67]Holmes, J. A., Wu, Z. J., and Griffith, B. P., “Investigation of fluid dynamics with a miniature mixed-flow blood pump,” Experiments in Fluid, Vol. 31, pp. 615-629, 2001.