In silico methods offer a valuable approach to predict localized deposition in the tracheobronchial
tree, important in the topical treatment of respiratory diseases and the systemic administration of
drugs with limited lung bioavailability. In this study, we examine the effect of extrathoracic airway
variation on regional deposition in order to assess whether standard mouth-throat models can
be adopted for more efficient predictions. Despite large qualitative differences in the extrathoracic
airways, deposition patterns and efficiencies in the tracheobronchial region remain largely unaffected
for particles smaller than 6 microns. The findings suggest that for drug delivery applications, standard
mouth-throat models could be adopted to predict deposition in the central airways.