Computational modelling and experimental validation of drug entrainment in a dry powder inhaler.

In a passive dry powder inhaler (DPI) a patient inhales to entrain drug powder. The goal of this study is to demonstrate experimentally that an Eulerian-Eulerian (EE CFD) computational fluid dynamics (CFD) method can accurately predict the entrainment of the dry powder formulation in DPIs. A CFD method that makes accurate predictions of the entrainment process can be applied in DPI design and optimization processes. Three different DPI entrainment geometries were tested. For each geometry, a transparent entrainment module was prepared. In each experiment, the chosen entrainment module was first filled with lactose powder and attached to an inhalation simulator (a computer controlled pump). The entrainment process was recorded with a high-speed camera. The resulting video footage was analysed and compared with CFD predictions. The observed distribution of powder in the entrainment compartment and the measured rate of drug entrainment were in good agreement with CFD predictions. Through a process of experimental validation, this study established the first demonstration that two-dimensional EE CFD methodology provides robust and accurate predictions of aerosol generation from DPI entrainment chambers. The findings support the wider application of EE CFD for the design optimization of DPI devices.