Simulation of the Dose from a Dry Powder Inhaler
Kyrre Thalberg1, Johan Remmelgas1, Duy Nguyen1, Ingela Niklasson Björn1 & Berend vad Wachem2
1Pharmaceutical Technology & Development, AstraZeneca GOT, SE 431 83 Mölndal, Sweden
2Imperial College, Dept of Mechanical Engineering, Exhibition Road, London SW7 2AZ, U K.
Fully coupled Computational Fluid Dynamics (CFD) – Discrete Element Method (DEM) simulations of adhesive mixture formulations were developed to capture dose emptying and dispersion from a dry powder inhaler (DPI). By a combination of macro-scale simulations, where all the carrier particles of a dose are included, and micro-scale simulations to account for the behaviour of the fine particles, a complete picture of the dose emptying and dispersion event was obtained.
As a starting point for the micro-scale models, fine particles are deposited onto a carrier particle to create a fines- carrier aggregate with a fines load of 5%. Five different micro-scale models account for interactions experienced by the fine particles. The output functions from the micro-model simulations are then tracked as scalar functions in the macro-scale CFD-DEM simulation, to get a complete view of the dosing event and to capture key performance parameters of DPI performance such as dose emptying time, fine particle fraction and the amount of particles retained in the device.
A key aim of this work was validation of the simulation model. For this purpose, adhesive mixtures were prepared and analysed using Next Generation Impactor as well as with time-resolved laser light scattering. Simulation data is seen to be in good agreement with experimental results. It can be concluded that the simulation model possesses the right physics and is able to capture key features of dose emptying and dispersion from a DPI such as the emptying times for fines and carrier particles and the fine particle fraction.