Chapter 10 Computational Analyses of Airway Flow and Lung Tissue Dynamics David W. Kaczka, Ashley A. Colletti, Merryn H. Tawhai, and Brett A. Simon Abstract The function of the mammalian respiratory system is the facilitation the transfer of gas exchange between the organism’s environment and its internal transport medium, the blood. Evolutionary processes have optimized the anatomic structure of the lung as a tree-like branching network of airways terminating in thin- walled elastic ducts and alveoli, where this gas exchange occurs. Both dissipative and elastic properties of the respiratory system contribute to its unique static and dynamic mechanical behavior. In this chapter, we will explore the various structural and functional relationships of the respiratory system, and review several compu- tational and modeling analyses that provide insight into the pathophysiology of common respiratory diseases. Particular emphasis is placed on studies that utilize imaging to help understand and/or validate the distributed regional nature of lung function. 10.1 Introduction The function of the mammalian respiratory system is to facilitate the transfer of gases between the organism’s environment and its internal transport medium, the blood. For biological efficiency, this gas exchange must occur over a tremendously large surface area during each breath. Evolutionary processes have optimized the anatomic structure of the lung as a reciprocating pump with a single intake/exhaust conduit, the trachea. The trachea leads to a tree-like branching network of air- ways terminating in thin-walled elastic ducts and alveoli, where most gas exchange occurs. The many branching airway segments provide viscous pathways for airflow, and the rapid, exponential expansion in effective airway cross-sectional area results in reduced gas velocities and changing flow regimes. The dissipative and elastic D.W. Kaczka (B ) Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA e-mail: dkaczka@bidmc.harvard.edu 375 K.B. Chandran et al. (eds.), Image-Based Computational Modeling of the Human Circulatory and Pulmonary Systems, DOI 10.1007/978-1-4419-7350-4_10, C  Springer Science+Business Media, LLC 2011