Numerical Simulations of Pharmaceutical Particles Depositing in the Human Respiratory System

Abstract

Millions of people world wide suffer from asthma, and respiratory diseases are one of the leading causes of death. Patients can be treated or relieved by inhalation of medicine, but the efficiency of the treatment is often dependent on on the local deposition of the inhaled drug. In this thesis, a virtual laboratory for simulating the deposition of pharmaceutical particles inhaled into the human respiratory system has been developed. The virtual laboratory is composed of the Navier-Stokes solver Oasis, a particle tracking framework, and several scripts for analyzing flow properties and post-processing of data. The Navier-Stokes solver Oasis has been thoroughly validated on problem spe- cific test cases, and has proven capable of simulating turbulent-like flows with high accuracy and minimal numerical dissipation, at a reasonable computational cost. Based on considerations on the flow properties in the human respiratory system, a particle motion algorithm has been developed and implemented in the framework of LagrangianParticles.py within the open source software fenicstools. The algorithm was verified second order accurate, and performed well under validation against established numerical and experimental results. The airflow in the human respiratory system for moderate and high inhalation rates was simulated, with inflow conditions that mimic the effect of a spray inhaler. The flow field was found to exhibit turbulent-like structures enhanced by asymmetries in the geometry. Finally, simulations of particles inhaled into the human respiratory system were performed, from which connections between particle size and deposition pattern were determined in overall good results reported in the literature.