טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentHofemeier Philipp
SubjectComputational Simulations of Inhaled Aerosols in the
Pulmonary Acinar Region
DepartmentDepartment of Biomedical Engineering
Supervisor Professor Josue Sznitman


Abstract

The surface area of the lung, and in particular of the pulmonary acinar region, constitutes the largest directly exposed to the external environment. Inhaled particles are acknowledged to potentially bypass the upper and extra-thoracic airways and reach the respiratory region of the lung. As a result, inhaled aerosols can either pose a health risk, e.g. sooty particles, or serve as therapeutic carriers. To date, it is widely acknowledged that inhaled particles ranging from 0.001 to 10 μm are able to reach and deposit in the respiratory region of the lungs. However, little is known about the local transport dynamics and deposition mechanisms of fine and ultrafine particles affected by diffusion, convection and sedimentation. Due to challenges in resolving the temporal and spatial properties of inhaled ultrafine particles in experiments, computational simulations of respiratory flows are an attractive strategy to uncover the complex dynamics governing aerosol transport in the acinar space.

Using computational fluid dynamics (CFD) simulations, we shed new light on the local transport characteristics of inhaled aerosols in acinar networks. In an at- tempt to understand and ultimately predict particle deposition outcomes, we modeled aerosol transport and deposition across a range of alveolar models and acinar tree sizes, under various breathing maneuvers. On a local alveolar scale, we unveil the effects of local breathing asynchronies underlining the intricate coupling of fluid flow and local lung motion. To uncover the interplay of intrinsic particle motion and complex, cyclic flow structures, we modeled particle transport in extensive 3D acinar morphologies and assessed temporal and spatial deposition metrics. Namely, we found that sub-micrometer particles around 0.5 μm in diameter exhibit the lowest deposition efficiencies and longest retention times. In contrast, micrometer and nanometer sized aerosols showed higher deposition efficiencies in the acinar model as they are affected by gravity and Brownian motion, respectively. Overall, our modeling strategies capture for the first time with high fidelity some of the anticipated dynamics of inhaled aerosols in the pulmonary acinar depths.