An Acoustic Study of Airways: Healthy and Pathological Models

Auscultation has been used qualitatively by clinicians for hundreds of years to diagnose and monitor the progression of pulmonary pathologies. Auscultation technique is based on the clinical evidence that the morphological and functional alterations of the respiratory system determined by diseases and injuries result in measurable changes in lung sounds generation and propagation. Centuries of clinical practice have led to an extensive cataloging of respiratory sounds and their alterations resulting from pathological conditions. However, the information collected over these years suffer from a lack of quantitative rigor as well as in a proper understanding and description of the phenomena involved. The effect of the pathology-induced structural and mechanical modifications on the sound transmission in the respiratory system has received arguably even less attention. A better understanding of sound propagation and of its alterations by pathological conditions or injuries might not only be valuable in terms of clinical interpretation and significance, but also pave the way for emerging imaging techniques such as magnetic resonance elastography. The long-term objective of this project is the creation of a computational model able to precisely mimic the creation, propagation and noninvasive measurement of naturally-occurring sounds associated airway physiology as well as the alterations induced by airways pathology. In this thesis, fitting within the general scope mentioned above, an analytical code was validated that can provide accurate and quantitative information about the sound propagation in the lower respiratory tract. The same model was modified to account for the morphometrical and mechanical alterations induced by specific pathologies allowing a comparison with the physiological condition.