Numerical simulation of the air flow and particulate deposition in emphysematous human acini
Creators: name: Dutta, Amitvikram
Publisher: name: University of British Columbia
Year: 2017

description: Emphysema, is a destructive process that leads to the permanent enlargement of air spaces within the parenchyma of the lung. Along with chronic bronchitis, emphysema forms one of the two components of Chronic Obstructive Pulmonary Disease (COPD), a serious condition that is responsible for severe limitation of expiratory airflow in its victims. The early stages of emphysema are charecterized by the destruction of tissue in the pulmonary acinus - the part of the lung airway tree responsible of gas exchange with the bloodstream. Little is known how emphysema affects airflow within the acinus especially in the early stages of the disease. In this thesis computational fluid dynamics simulations are performed of airflow in a mathematically-derived model of a section of the pulmonary acinus. The computational domain consists of two generations of the acinus with alveolar geometries approximated as closely-packed, fourteen-sided polygons. Emphysema, is a destructive process that leads to the permanent enlargement of air spaces within the parenchyma of the lung. Along with chronic bronchitis, emphysema forms one of the two components of Chronic Obstructive Pulmonary Disease (COPD), a serious condition that is responsible for severe limitation of expiratory airflow in its victims. The early stages of emphysema are charecterized by the destruction of tissue in the pulmonary acinus - the part of the lung airway tree responsible of gas exchange with the bloodstream. Little is known how emphysema affects airflow within the acinus especially in the early stages of the disease. In this thesis computational fluid dynamics simulations are performed of airflow in a mathematically-derived model of a section of the pulmonary acinus. The computational domain consists of two generations of the acinus with alveolar geometries approximated as closely-packed, fourteen-sided polygons. Physiologically realistic flow rates and wall motions are used to capture the acinar flow during the inspiratory and expiratory phases of the breathing cycle. The effects of emphysema on the airway wall motion, flow rates, and septal destruction are simulated at various stages of the disease's progression to identify the effect on the flow in the acinar region. Parametric studies are presented to independently assess the relative influence of septal destruction and the emphysematous degradation of airway motion and flow rates. The results illustrate that septal destruction lowers the flow resistance through the alveolar ducts but has little influence on the mass transport of oxygen into the alveoli. Septal destruction has a net effect on the flow field by favouring the development of recirculatory flow patterns in individual alveoli. The effects of the gradually advancing emphysema on the deposition of micron-sized particles in the acinus are also studied. The simulations are categorized according to particle size and the relative orientation of the gravitational vector to the incoming flow. Emphysematous destruction increases the deposition of particles in affected ducts, with the greatest increase occurring for the larger particle size when the gravity vector is oriented tangential to the incoming flow.