Acoustic simulation of a patient's obstructed airway

Abstract

This research focuses on the numerical simulation of stridor; a high pitched, abnormal noise, resulting from turbulent airflow and vibrating tissue through a partially obstructed airway. Characteristics of stridor noise are used by medical doctors as indication for location and size of the obstruction. The relation between type of stridor and the various diseases associated with airway obstruction is unclear; therefore, simply listening to stridor is an unreliable diagnostic tool. The overall aim of the study is to better understand the relationship between characteristics of stridor noise and localization and size of the obstruction. Acoustic analysis of stridor may then in future simplify the diagnostic process, and reduce the need for more invasive procedures such as laryngoscopy under general anesthesia. In this paper, the feasibility of a coupled flow, acoustic and structural model is investigated to predict the noise generated by the obstruction as well as the propagation of the noise through the airways, taking into account a one-way coupled fluid, structure, and acoustic interaction components. The flow and acoustic solver are validated on a diaphragm and a simplified airway model. A realistic airway model of a patient suffering from a subglottic stenosis, derived from a real computed tomography scan, is further analyzed. Near the mouth, the broadband noise levels at higher frequencies increased with approximately 15–20 dB comparing the stridorous model with the healthy model, indicating stridorous sound.

Keywords::

• fluid-structure-acoustic interaction
• human airway
• stridor
• large eddy simulation
• Ffowcs-Williams and Hawkings analogy

Acknowledgements

The authors would like to thank Chris Lacor, from Vrije Universiteit Brussel, for providing the model of the simplified airway. Also, the authors would like to thank Wim Vos from FluidDA, who has created the CAD model from a CT scan, which is used here as the realistic airway model. All these simulations required much computational effort, which has been made available by the Aerodynamics department of the Faculty of Aerospace Engineering, Delft University of Technology, the Netherlands.

Conflict of interest disclosure statement

No potential conflict of interest was reported by the authors.