A Numerical Simulation of Inspiratory Airflow in Human Airways during Exercise at Sea Level and at High Altitude

Document Type: Research Paper

Authors

Department of Mathematics, Indian Institute of Technology Roorkee, Roorkee -247667 (Uttarakhand) India

Abstract

At high altitudes, the air pressure is much lower than it is at sea level and contains fewer oxygen molecules and less oxygen is taken in at each breath. This requires deeper and rapid breathing to get the same amount of oxygen into the blood stream compared to breathing in air at sea level. Exercises increase the oxygen demand and make breathing more difficult at high altitude. In this study, a numerical simulation of inspiratory airflow in a three-dimensional bifurcating human airways model (third to sixth generation) during exercise at sea level and at high altitude was performed. The computational fluid dynamics (CFD) solver FLUENT was used to solve the governing equations for unsteady airflow in the model. Flow velocity, pressure, and wall shear stress were obtained from the simulations with the two breathing conditions. The result of this study quantitatively showed that performing exercise with a given work rate at high altitude increased inspiratory airflow velocity, pressure, and wall shear stress more than that at sea level in the airway model. The ranges of the airflow fields were also higher at high altitude than sea level. The simulation results showed that there were no significant differences in flowing pattern for the two breathing conditions.

Keywords

Main Subjects

[1] Cibella, F., Cuttitta, G., Kayser, B., Narici, M., Romano, S., Saibene, F., Respiratory mechanics during exhaustive submaximal exercise at high altitude in healthy humans, Journal of Physiology 494 (1996) 881-890.

[2] Aiken, M., Altitude Training for Everyone, 2013, https://www.runnersworld.com/race-training/altitude-training-for-everyone.

[3] Wehrlin, J.P., Hallén, J., Linear decrease in VO2max and performance with increasing altitude in endurance athletes, European Journal of Applied Physiology 96 (2005) 404-412.

[4] Sheel, A.W., MacNutt, M.J., Querido, J.S., The pulmonary system during exercise in hypoxia and the cold, Experimental Physiology 95 (2010) 422-430.

[5] Augusto, L.L.X., Lopes, G.C., Gonçalves, J.A.S., A CFD study of deposition of pharmaceutical aerosols under different respiratory conditions, Brazilian Journal of Chemical Engineering 33 (2016) 549-558.

[6] Weibel, E.R., Morphometry of the Human Lung. Springer Verlag, New York, 1963.

[7] Deng, Q., Ou, C., Chen, J., Xiang, Y., Particle deposition in tracheobronchial airways of an infant, child and adult, Science of the Total Environment 612 (2017) 339-346.

[8] Srivastav, V.K., Paul, A.R., Jain, A., Computational fluid dynamics study of airflow and particle transport in third to sixth generation human respiratory tract, International Journal of Emerging Multidisciplinary Fluid Sciences 3(4) (2012) 227-234.

[9] Hegedűs, C.J., Baláshá, Z.Y.I., Farkas, Á., Detailed mathematical description of the geometry of airway bifurcations, Respiratory Physiology & Neurobiology 141 (2004) 99-114.

[10] Ou, C., Deng, Q., Liu, W., Numerical simulation of particle deposition in obstructive human airways, Journal of Central South University 19 (2012) 609-614.

[11] Ou, C., Li, Y., Wei, J., Yen, H.L., Deng, Q., Numerical modeling of particle deposition in ferret airways: A comparison with humans, Aerosol Science and Technology 51(4) (2017) 477-487.

[12] Liu, Y., So, R.M.C., Zhang, C.H., Modeling the bifurcating flow in a human lung airway. Journal of Biomechanics 35 (2002) 477-485.

[13] Gemci, T., Ponyavin, V., Chen, Y., Chen, H., Collins, R., Computational model of airflow in upper 17 generations of human respiratory tract, Journal of Biomechanics 41 (2008) 2047-2054.

[14] Rahimi-Gorji, M., Gorji, T.B., Gorji-Bandpy, M., Details of regional particle deposition and airflow structures in a realistic model of human tracheobronchial airways: two-phase flow simulation. Computers in Biology and Medicine 74 (2017) 1-17.

[15] Qi, S., Zhang, B., Teng, Y., Li, J., Yue, Y., Kang, Y., Qian, W., Transient dynamics simulation of airflow in a CT-scanned human airway tree: more or fewer terminal bronchi? Computational and Mathematical Methods in Medicine 2017(3) (2017) 1-14.

[16] Elcner, J., Lizal, F., Jedelsky, J., Jicha, M., Chovancova, M., Numerical investigation of inspiratory airflow in a realistic model of the human tracheobronchial airways and a comparison with experimental results, Biomechanics and Modeling in Mechanobiology 15(2) (2016) 447–469.

[17] Johnson, T., Biomechanics and Exercise Physiology: Quantitative Modeling, Second edition, CRC press, New York, 2007.