Comparing MDI and DPI aerosol deposition using in vitro experiments and a new stochastic individual path (SIP) model of the conducting airways.

PURPOSE: Deposition characteristics of MDI and DPI aerosols were compared throughout the conducting airways for the first time using a combination of in vitro experiments and a newly developed stochastic individual path (SIP) model for different inhalation profiles. METHODS: In vitro experiments were used to determine initial particle distribution profiles and to validate computational fluid dynamics (CFD) model results for a MDI and DPI delivering the same dose of drug in a geometry of the mouth-throat and tracheobronchial airways. The validated CFD model was then used to predict the transport and deposition of the drug using correct and incorrect inhalation profiles for each inhaler. RESULTS: The MDI delivered approximately two times more drug to the tracheobronchial region compared with the DPI for both correct and incorrect inhalation profiles. Errors in inhalation reduced the deposited tracheobronchial dose by approximately 30% for both inhalers. The DPI delivered the largest dose to the mouth-throat (~70%) and the MDI delivered the largest dose to the alveolar airways (~50%). CONCLUSIONS: The developed in silico model provides new insights into the lung delivery of pharmaceutical aerosols and can be applied in future studies in combination with pharmacokinetic analysis to establish bioequivalence between devices.