Date of Award

12-30-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Systems Engineering

First Advisor

Jinxiang Xi

Abstract

Determining how many inhaled aerosols deposit in human respiratory airways and where they deposit (i.e., respiratory dosimetry) are of critical importance in a number of fields. Applications of respiratory dosimetry modeling include evaluating health effects of inhaled pollutants, establishing environmental exposure standards, and developing effective techniques for delivering pharmaceutical aerosols to the lung. However, the manifold characteristics of aerosols coupled with the complexity of respiratory tract make such analysis a challenging task as well as a highly multidisciplinary effort, entailing expertise from medicine, engineering, and physiology. In this study, three major factors that affect particle transport and depositions were systematically investigated, namely, (1) the properties of inhaled particles, (2) the respiratory physiology, and (3) the breathing conditions. The interplay among these three factors will be emphasized. These results are intended to provide guidance in making appropriate dose-response and health effects predictions of inhaled medications or toxicants. To begin with, patient-specific physiologically realistic reparatory airway models have been developed based on medical imaging such as CT or MRI. These models were either manufactured into a solid cast for in vitro experimental studies, or meshed with high-quality computational elements for numerical analysis. Employing these image-based airway models, six projects have been carried out, with each addressing one aspect of the respiratory aerosol dynamics. Firstly, the effects of anatomical details of the upper airway on aerosol depositions were examined. Secondly, micron particle depositions were studied both experimentally and numerically in the nasal airway of a 5-year-old child. The third study simulated the dynamic growth of hygroscopic particles under different thermo-humidity conditions, which could dramatically change the deposition mechanisms. The developmental respiratory anatomy from infancy to adult was characterized in the forth study. In the fifth project, the head orientation effects on face deposition and lung delivery efficiency were evaluated during inhalation therapy for infants with a nebulizer hood. The sixth project investigated the feasibility of using aerosol breath tests to diagnose the location and severity of obstructive lung diseases. The dynamic interactions between inhaled aerosols, respiratory physiology and breathing activities that might be used to improve drug delivery efficiency will be discussed. I will include with future studies that is promising in diagnosis of respiratory diseases with aerosol test and acoustic analysis.

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