Deposition of inertial size particles in the replicate models of human extrathoracic airways simulating inhalation of therapeutic aerosols

The dry powder inhalers are a convenient alternative therapeutic aerosol delivery system for patients with respiratory diseases that are incapable of using metered dose inhalers properly. Investigating the deposition efficiency and pattern of inhaled particles in the upper oral airways may provide information on specific inhaler design characteristics which can be used to enhance the penetration of dry powder or other therapeutic aerosols when inhaled.;This study presents in vitro measurements of the total and local particle depositions in the adult human oral-pharyngeal-laryngeal airway replicate models. Three factors--particle aerodynamic diameter, inspiratory flow rate, and mouth opening size in terms of the distance between the upper and lower teeth caused by the inhalation mouth piece--were examined to determine their effects on the total particle deposition in three clear rubber cast models. A vacuum pump was used to draw aerosols of 2, 4, and 8 ;This research demonstrated that the total particle deposition increased significantly as particle aerodynamic diameter and/or air flow rate increased. These results confirmed the inertial impaction as the dominant mechanism by which the particles of inertial sizes (1;The results of the local deposition study showed that significant particle deposition occurred in the anterior oral region and the oropharynx for inertial size particles, particularly larger than 4 ;While the design of a larger mouth piece on the inhalation devices can be recommended for patients to achieve a greater penetration of therapeutic aerosols into the deeper lung, it must be cautioned that the results presented here should be validated by further research on human subjects to better understand the deposition efficiency and pattern of therapeutic aerosols in human oral airways.