Respiratory tract acoustical modeling and measurements

V. Paul Harper, Purdue University

Abstract

With the emerging use of tracheal sound analysis to detect and monitor respiratory tract changes such as those found in asthma and obstructive sleep apnea, there is a need to link the attributes of these easily measured sounds first to the underlying anatomy, and then to specific pathophysiology. To begin this process, we have developed a model of the acoustic properties of the entire respiratory tract (supraglottal plus subglottal airways) over the frequency range of tracheal sound measurements, 100 to 3,000 Hz. The respiratory tract is represented by a transmission line acoustical analogy with varying cross sectional area, yielding walls, dichotomous branching in the subglottal component, and airflow related acoustical sources distributed throughout the entire respiratory tract. The model predicts the location in frequency of the natural acoustic resonances for components and the entire tract. Individually, the supra and subglottal portions of the model predict well the distinct locations of the spectral peaks (formants) from speech sounds (such as /a/) measured at the mouth and the trachea, respectively, in healthy subjects. When combining the supra- and subglottic portions to form a complete tract model, the predicted peak locations compare favorably with those of tracheal sounds measured during normal breathing. In addition, the model predicts changes in the spectral amplitude of tracheal sounds that are observed experimentally for varying degrees of tracheal obstruction and volumetric airflow rates. This study provides the first insights into the complex relationships between the spectral peaks and amplitudes of tracheal sounds, volumetric airflow, and the underlying anatomy of the respiratory tract.

Degree

Ph.D.

Advisors

Wodicka, Purdue University.

Subject Area

Biomedical research|Electrical engineering

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