DOI
https://doi.org/10.25772/9G8C-F307
Defense Date
2011
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Mechanical and Nuclear Engineering
First Advisor
Philip Longest
Abstract
Predicting vapor transport and aerosol dynamics in the respiratory airways is important for analyzing both environmental exposure and respiratory drug delivery. A large number of analytical models, computational studies, and experiments on vapor and aerosol transport in the respiratory tract have been conducted previously. However, a number of critical questions remain unanswered. In this study, computational fluid dynamics (CFD) is primarily employed with frequent comparisons to existing and new experimental data sets to address previously unanswered issues related to the transport of vapors and aerosol in the respiratory tract. The three objectives of this study are further described below. Objective 1: A CFD model was developed to predict the transient absorption of inhaled vapors in the respiratory tract. Results indicated that transient absorption can significantly influence the transport and uptake of vapors in the walls of the conducting airways. Objective 2: The concept of enhanced condensational growth (ECG) applied to respiratory drug delivery was tested in a representative airway model extending from the oral cavity to the end of the tracheobronchial (TB) airways. Results indicated that ECG is an effective method to provide near full lung retention of the aerosol. The CFD results also indicated that the ECG delivery approach under transient inhalation conditions increased aerosol deposition in the TB airways by only a small amount, as compared with steady state conditions. Objective 3: The effect of transient waveforms on the transport and deposition of pharmaceutical aerosols from inhalers in the upper airways was considered. Results indicated that the CFD model predictions matched the in vitro experiments to a high degree. The CFD results also indicated that it was critical to consider transient inhalation effects when assessing aerosol deposition. The stochastic individual path (SIP) modeling approach was then introduced and implemented to evaluate the transport and deposition of pharmaceutical aerosols from inhalers in medium and small TB airways. Results indicated that steady state inhalation could be used to predict deposition efficiencies in the TB airways between the 4th branch (B4) and the bronchioles (B15).
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
May 2011