Glottal motion and its impact on inhaled aerosol deposition in upper airways
Résumé
During inhaled therapies for the treatment of pulmonary diseases, upper airways (UA) anatomic arrangement can act as an unwanted filter, which limits the amount of drug delivered to the lungs. The minimal UA constriction is defined by the vocal folds aperture within the larynx, called the glottis. This anatomical singularity yields to a complex jet-like tracheal flow, which can be determinant on particle transport and deposition by inertial impaction. The present study aims to characterize the glottal dynamics during in vivo human breathing, and to predict the effect of a realistic mobile glottis on the aerosol filtering in the larynx using CFD modeling. Firstly, the glottal dynamics during eupnea, tachypnea and hyperpnea breathing were investigated using synchronized video recording of laryngofibroscopic examination and oral airflow measurements. Direct measurement of subglottal air pressure was also performed to determine transglottal pressure drop changes. Glottal geometrical variations were then deduced from an image processing analysis and used to develop a 3D dynamic model of the glottal aperture. Finally, numerical two-phase flow simulations were conducted using experimental unsteady airflow conditions, for both motionless and realistic glottal configurations. The results of the experimental measures show that the glottal geometry observed during a breathing cycle can be extremely variable depending on the respiratory phase, volume magnitude and frequency. Inter-subject variability of the identified glottal motions is also established. The CFD simulations demonstrate that the glottal geometry variations strongly influence the laryngeal jet dynamics, transglottal pressure drop and aerosol deposition within the laryngeal area.