本研究使用數值方法來模擬呼吸原理與粒子在分歧氣管之運動模擬。利用改變雷諾數(Reynolds number)和沃斯理數(Womersley number)來模擬不同的呼吸狀態。
以一個呼吸週期(T)來看,吸氣過程時,在T/4和T/2間,氣管的外側邊壁開始產生迴流區域,
吸入的氧氣被擠壓到氣管的內側邊壁。呼氣過程時,在3T/4和T間,氣管的分歧區域和外側的邊壁上開始產生迴流區域,氧氣被滯留到分歧管內側邊壁和外側的邊壁上,下一次吸氣時再將滯留的氧氣往分歧管內部推進。隨著不斷的呼吸,使得吸入的氧氣能夠逐漸的進入氣管內層,完成氣體交換。

在觀察不同呼吸狀態下的呼吸效率發現,若是增加吸入氣體的體積,呼吸效率會隨之增加。
若是降低呼吸的頻率,呼吸效率也會隨之增加。粒子在分歧氣管之運動模擬結果觀察出,
呼氣時,會有部分的微粒子沈積在氣管的分歧區域表面和氣管管壁表面上,若是降低呼吸頻率,微粒子在氣管內沈積率會隨之增加。若是減少吸入的呼吸流量,微粒子在氣管內的沈積效率也會隨之增加。

Numerical approaches were performed to simulate the particle motions in bifurcated lung airways and phenomena of pulmonary.Nondimensional parameters, Reynolds number and Womersley number, were used to observe effects breathing patterns on pulmonary efficiency and particle motions.When we observe pulmonary phenomena in airways in a breath cycle(T), separation regions formed on the side walls of the bifurcations were observed between T/4 and T/2 during inspiration.
The incoming O2 was carried to the regions near inner walls of the bifurcations.During expiration, separation regions formed at two different places were observed between 3T/4 and T.The first one was found at the intersection between daughter and parent tubes, and the other one appeared downstream in the regions near the side walls of bifurcations.Some of O2 were trapped in the separation regions.
Subsequently, in the next inspiration, the trapped O2 was carried further downstream the alveoli.

Comparing the pulmonary efficiency among different breathing condition, we found that, increasing respiratory volume could enhance the breathing efficiency.However, decreasing oscillation frequency may also improve the breathing efficiency.Comparing the particle deposition efficiency among a variety of breathing condition, it was found that a few of particles deposit on the intersection surface between parent and daughter tubes and the surface of bifurcations.Decreasing in breathing frequency could improve the particle deposition efficiencies.Nonethless, decreasung respiratory volume may enhance the particle deposition efficiency.

[1] Weibel, B.J., 1963, Morphometry of the Human Lung, Academic Press, New York, USA.
[2] Pedley, T.J., 1977, Pulmonary fluid dynamics. Annu. Rev. Fluid Mech 9, 229-274.
[3] Grotberg, J.B., 1994, Pulmonary flow and transport phenomena. Annu. Rev. Fluid Mech 26, 529-571.
[4] Ukil, S. and Reinhardt, J. M., 2004, Smoothing lung segmentation surfaces in 3D x-ray CT images using anatomic guidance. Proceedings of SPIE - The International Society for Optical Engineering, Progress in Biomedical Optics and Imaging - Medical Imaging2004: Imaging Processing 5370, 1066-1075,International Society for Optical Engineering, Bellingham, WA 98227-0010, USA.
[5] Kiraly, A.P., Higgins, W.E., Hoffman, E.A., McLennan, G. and Reinhardt, J.M., 2002, 3D human airway segmentation for virtual bronchoscopy. Physiology and Function From Multidimensional Images 4683, 16-29.
[6] Aykac, D., Hoffman, E.A., McLennan, G. and Reinhardt, J.M., 2003, Segmentation and analysis of the human airway tree from tree-dimensional x-ray CT images. IEEE Transactions on Medical Imaging 22, 940-950.
[7] Li, B. J., Christensen, G. E., Hoffman, E.A., McLennan, G. and Reinhardt, J.M., 2003, Establishing a normative atlas of the human lung: intersubject warping and registration of volumetric CT images. Acad Radiol 10, 255-265.
[8] Mochizuki, S., 2003, Convective mass transport during ventilation in a model of branched airways of human lungs. Proceedings of Pacific Symposium on Flow Visualization and Image Processing 4, Chamonix Mont-Blanc, France.
[9] Horikomi, T. and Watanabe, T., 2003, Diffusion enhancement in high frequency ventilation(HFV) in a double-bifurcation airway model. Proceedings of Pacific Symposium on Flow Visualization and Image Processing 4, Chamonix Mont-Blanc, France.
[10] Heyder, J., Gebhart, J., Rudolf, G., Schiller, C. F. and Stahlhofen, W., 1986, Deposition of particles in the human respiratory tract in the size range 0.005-15μm. J. Aerosol Sci. 17, 811-825.
[11] Zhang, Z., Kleinstreuer, C. and Kim, C.S., 2002, Gas-solid two-phase flow in a triple bifurcation lung airway model. International Journal of Multiphase Flow 28, 1021-1046.
[12] Zhang, Z. and Kleinstreuer, C., 2003, Species heat and mass transfer in a human upper airway model. International Journal of Heat and Mass Transfer 46, 4755-4768.
[13] Brucker, Ch. and Schroder, W., 2003, Flow visualization in a model of the bronchial tree in the human lung airways via 3-D PIV. Proceedings of Pacific Symposium on Flow Visualization and Image Processing 4, Chamonix Mont-Blanc, France.
[14] Weibel, E.R., 1991, Design of airway and blood vessels considered as branching trees. The Lung, eds. Crystal, R.G., West, J.B. et al., 1, Raven Press, 711-720, New York, USA.
[15] Kim, C.S., Brown, L.K., Lewars, G.G., Sackner, M.A., 1983, Deposition of aerosol particles and flow resistance in mathematical and experimental airway. Journal of Applied Physiology: Respiration Environment Exercise Physiology 55, 154-163.
[16] Hofmann, W., Balashazy, I., Koblinger, L., 1995, The effect of gravity on particle deposition patterns in bronchial airway bifurcations. J. Aerosol Sci. 26, 1161-1168.
[17] Reist, P. C., 1993, Aerosol Science and Technology, McGraw-Hill, Inc.
[18] Zhang, Z. and Kleinstreuer, C., 2004, Airflow structures and nano-particle deposition in a human upper airway model. Journal of Computational Physics 198, 178-210.