Düşük Reynolds sayılı alveolar akışta partikül boyutunun aerosol dinamikleri üzerine etkisinin sayısal olarak incelenmesi

Yıl 2021, Cilt: 11 Sayı: 3, 805 - 814, 15.07.2021

Doğan Çiloğlu

https://doi.org/10.17714/gumusfenbil.864791

Öz

Akciğer hastalıklarında etkili bir tedavi yönteminin geliştirilmesi ve ilaç taşınımının iyileştirilmesi açısından akciğerlerin asiner bölgesindeki hava akışının ve solunan farmasötik veya zararlı partiküllerin taşınmasının incelenmesi çok önemlidir. Bu çalışmada, insan akciğerinin asiner bölgesinde etrafı alveol keseleri ile çevrilmiş bir respiratuar bronşiol modeli üzerinde alveolar hava akışı ve farklı boyutlardaki partiküllerin aerosol dinamikleri üzerine etkisi hesaplamalı akışkanlar dinamiği (CFD) kullanılarak sayısal olarak incelenmiştir. Sayısal simülasyonlar, çoklu nefes periyotları ve üç farklı solunum şartı (düşük, normal ve ağır solunum) için yapılmıştır. Her bir akış durumunda model girişinden hesap alanına farklı çaplara sahip aerosol partikülleri salınmış ve yörüngeleri sayısal olarak takip edilmiştir. Sonuçlar, hareketli alveol duvarları sayesinde alveol çukurlarına hava ve partikül girişinin olduğunu göstermiştir. Alveol çukurunda meydana gelen resirkülasyonlu akış yapılarının partikül dinamiklerini karakterize ettiği belirlenmiştir. Elde edilen sonuçlara göre model içerisinde kalan aerosol miktarı, partikül boyutu ve akış debisiyle azalmıştır. 7 µm’nin üzerinde çapa sahip aerosol partiküllerinin kanal cidarlarında ve 5 µm’nin altındaki partiküllerin ise alveol boşluklarında biriktiği belirlenmiştir. Sonuç olarak bu çalışma, solunan farmasötik veya zararlı partiküllerin alveolar bölgede davranışlarıyla ilgili önemli fizyolojik sonuçlar sunmaktadır.

Anahtar Kelimeler

Asiner akış dinamiği, Düşük Reynolds sayılı akış, Resirkülasyon, Sonlu elemanlar

Numerical analysis of the particle size effect on aerosol dynamics in low Reynolds number alveolar flow

Öz

In order to develop an effective treatment method and improve drug delivery in lung diseases, it is very important to examine the airflow and the transport of inhaled pharmaceutical or harmful particles in the acinar region of the lungs. In this study, the alveolar airflow and the effect of particles of different sizes on aerosol dynamics were numerically investigated on a respiratory bronchiole model surrounded by alveolar sacs in the acinar region of the human lung using computational fluid dynamics (CFD). Numerical simulations were made for multiple breathing periods and three different respiratory conditions (i.e, low, normal and heavy breathing). In each flow situation, aerosol particles with different diameters from the model entry to the computational domain were released and their trajectories were tracked numerically. The results showed that there was air and particle entry into the alveolar cavities due to the movable alveolar walls. It was determined that the recirculating flow structures occurring in the alveolus characterize the particle dynamics. According to the results, the amount of aerosol remaining in the model decreased with particle size and flow rate. It was also found that aerosol particles with a diameter of more than 7 µm deposited on the duct walls and the particles below 5 µm in the alveolar cavities. Consequently, this study provides the important physiological results regarding the behavior of inhaled pharmaceutical or harmful particles in the alveolar region.

Anahtar Kelimeler

Acinar fluid dynamics, Low Reynolds number flow, Recirculation, Finite element

Kaynakça

• Bennett, W.D. and Smaldone, G.C. (1985). Use of aerosols to estimate mean air-space size in chronic obstructive pulmonary disease. Journal of Applied Physiology, 64(4), 1554-1560. https://doi.org/10.1152/jappl.1988.64.4.1554
• Berg, E.J. and Robinson, R.J. (2011). Stereoscopic particle image velocimetry analysis of healthy and emphysemic alveolar sac models. Journal of Biomechanical Engineering, 133(6), 061004. https://doi.org/10.1115/1.4004251
• Ciloglu, D. (2020). A numerical study of the aerosol behavior in intra-acinar region of a human lung. Physics of Fluids, 32(10), 103305. https://doi.org/10.1063/5.0024200
• Darquenne, C. and Prisk, G.K. (2003). Effect of gravitational sedimentation on simulated aerosol dispersion in the human acinus. Journal of Aerosol Science, 34(4), 405-418. https://doi.org/10.1016/s0021-8502(02)00187-8
• Darquenne, C. and Prisk, G.K. (2004). Effect of small flow reversals on aerosol mixing in the alveolar region of the human lung. Journal of Applied Physiology, 97, 2083-2089. https://doi.org/10.1152/japplphysiol.00588.2004
• Darquenne, C. and Paiva, M. (1996). Two- and three-dimensional simulations of aerosol transport and deposition in alveolar zone of human lung. Journal of Applied Physiology, 80(4), 1401-1414. https://doi.org/10.1152/jappl.1996.80.4.1401
• Darquenne, C., Harrington, L. and Prisk, G.K. (2009). Alveolar duct expansion greatly enhances aerosol deposition: a three-dimensional computational fluid dynamics study. Philosophical Transactions of the Royal Society A, 367, 2333-2346. https://doi.org/10.1098/rsta.2008.0295
• Fishler, R., Hofemeier, P., Etzion, Y., Dubowski, Y. and Sznitman, J. (2015). Particle dynamics and deposition in true-scale pulmonary acinar models. Scientific Reports, 5, 14071. https://doi.org/10.1038/srep14071
• George, P.M., Wells, A.U. and Jenkins, R.G. (2020). Pulmonary fibrosis and COVID-19: the potential role for antifibrotic therapy. Lancet Respiratory Medicine, 2600(20), 1-9. https://doi.org/10.1016/S2213-2600(20)30225-3
• Harding, E.M. and Robinson, R.J. (2010). Flow in a terminal alveolar sac model with expanding walls using computational fluid dynamics. Inhalation Toxicology, 22(8), 669-678. https://doi.org/10.3109/08958371003749939
• Harrington, L., Prisk, G.K. and Darquenne, C. (2006). Importance of the bifurcation zone and branch orientation in simulated aerosol deposition in the alveolar zone of the human lung. Journal of Aerosol Science, 37(1), 37-62. https://doi.org/10.1016/j.jaerosci.2005.03.005
• Henry, F.S., Butler, J.P. and Tsuda, A. (2002). Kinematically irreversible acinar flow: A departure from classical dispersive aerosol transport theories. Journal of Applied Physiology, 92(2), 835-845. https://doi.org/10.1152/japplphysiol.00385.2001
• Henry, F.S., Laine-Pearson, F.E. and Tsuda, A. (2009). Hamiltonian chaos in a model alveolus. Journal of Biomechanical Engineering, 131(1), 011006. https://doi.org/10.1115/1.2953559
• Heyder, J. (2004). Deposition of inhaled particles in the human respiratory tract and consequences for regional targeting in respiratory drug delivery. Proceedings of the American Thoracic Society, 1(4), 315-320. https://doi.org/10.1513/pats.200409-046TA
• Heyder, J., Blanchard, J.D., Feldman, H.A. and Brian, J.D. (1988). Convective mixing in human respiratory tract: Estimates with aerosol boli. Journal of Applied Physiology, 64(3), 1273-1278. https://doi.org/10.1152/jappl.1988.64.3.1273
• Katan, J.T., Hofemeier, P. and Sznitman, J. (2016). Computational models of inhalation therapy in early childhood: Therapeutic aerosols in the developing acinus. Journal of Aerosol Medicine and Pulmonary Drug Delivery, 29(3), 288-298. https://doi.org/10.1089/jamp.2015.1271
• Knudsen, L., Weibel, E.R., Gundersen, H.J.G., Weinstein, F.V. and Ochs, M. (2010). Assessment of air space size characteristics by intercept (chord) measurement: An accurate and efficient stereological approach. Journal of Applied Physiology, 108(2), 412-421. https://doi.org/10.1152/japplphysiol.01100.2009
• Kumar, H., Tawhai, M.H., Hoffman, E.A. and Lin, C.L. (2009). The effects of geometry on airflow in the acinar region of the human lung. Journal of Biomechanics, 42(11), 1635-1642. https://doi.org/10.1016/j.jbiomech.2009.04.046
• Kumar, H., Tawhai, M.H., Hoffman, E.A. and Lin, C.L. (2011). Steady streaming: A key mixing mechanism in low-Reynolds-number acinar flows. Physics of Fluids, 23(4), 1-21. 41902. https://doi.org/10.1063/1.3567066
• Lee, D.Y. and Lee, J.W. (2003). Characteristics of particle transport in an expanding or contracting alveolated tube. Journal of Aerosol Science, 34(9), 1193-1215. https://doi.org/10.1016/S0021-8502(03)00097-1
• Ottino, J.M., Leong, C.W., Rising, H. and Swanson, P.D. (1988). Morphological structures produced by mixing in chaotic flows. Nature, 333(6172), 419-425. https://doi.org/10.1038/333419a0
• Sarangapani, R. and Wexler, A.S. (1999). Modeling aerosol bolus dispersion in human airways. Journal of Aerosol Science, 30(10), 1345-1362. https://doi.org/10.1016/S0021-8502(99)00027-0
• Sznitman, J., Heimsch, T., Wildhaber, J.H., Tsuda, A. and Rosgen, T. (2009). Respiratory flow phenomena and gravitational deposition in a three-dimensional space-filling model of the pulmonary acinar tree. Journal of Biomechanical Engineering, 131(3), 031010. https://doi.org/10.1115/1.3049481
• Sznitman, J., Sutter, R., Altorfer, D., Stampanoni, M., Rosgen, T. and Schittny, J.C. (2010). Visualization of respiratory flows from 3D reconstructed alveolar airspaces using X-ray tomographic microscopy. Journal of Visualization, 13(4), 337-345. https://doi.org/10.1007/s12650-010-0043-0
• Talaat, K. and Xi, J. (2017). Computational modeling of aerosol transport, dispersion, and deposition in rhythmically expanding and contracting terminal alveoli. Journal of Aerosol Science, 112, 19-33. https://doi.org/10.1016/j.jaerosci.2017.07.004
• Tawhai, M.H. and Lin, C.-L. (2010). Image-based modeling of lung structure and function. Journal of Magnetic Resonance Imaging, 32, 1421-1431. https://doi.org/10.1002/jmri.22382
• Tsuda, A., Henry, F.S. and Butler, J.P. (1985). Chaotic mixing of alveolated duct flow in rhythmically expanding pulmonary acinus. Journal of Applied Physiology, 79(3), 1055-1063. https://doi.org/10.1152/jappl.1995.79.3.1055
• Tsuda, A., Rogers, R.A., Hydon, P.E. and Butler, J.P. (2002). Chaotic mixing deep in the lung. Proceedings of the National Academy of Science USA, 99(15), 10173-10178. https://doi.org/10.1073/pnas.102318299
• Xia, G, Tawhai, M.H., Hoffman, E.A. and Lin, C.-L. (2010). Airway wall stiffness and peak wall shear stress: A fluid-structure interaction study in rigid and compliant airways. Annals of Biomedical Engineering, 38(5), 1836-1853. https://doi.org/10.1007/s10439-010-9956-y
• Xia, G. and Lin, C.-L. (2008). An unstructured finite volume approach for structural dynamics in response to fluid motions. Computers & Structures, 86(7), 684-701. https://doi.org/10.1016/j.compstruc.2007.07.008