Effect of turbulent kinetic energy on dry powder inhaler performance

Abstract

Dry powder inhalers (DPIs) have been extensively used for delivering medication to the lungs. Different designs of DPI devices affect the aerosolization processes of the drug particles. The processes cannot be easily visualized in experiments, thus computational fluid dynamics were used to investigate the turbulence kinetic energy and particle impaction. In this research, 3 size ranges of lactose carrier and the Cyclohaler® and Inhalator® devices were used as models for the computational simulations. The velocity vector, the turbulence kinetic energy (TKE) and particle trajectory were obtained. An aerosol dispersion experiment was performed using the Andersen Cascade Impactor. The TKE was directly related to the flow-rate. The TKE in the Cyclohaler® was lower than that in the Inhalator® due to its narrow geometry and this resulted in a high velocity air-flow. In the Cyclohaler® the probability of deagglomeration by impaction was high because of the cyclone-like design while the cross grid of the Inhalator® was an important factor for deagglomeration of the particles. The FPF varied from 7 to 30% and the FPF increased as the flow-rate increased. The MMAD was in the range of 4–6μm. The carrier size also affected the probability of deagglomeration at 60 and 90L/min, but not at 30L/min. In summary, maximizing the TKE and the particle impaction rate by adding a grid and providing a cyclone-like design was key factor to achieve a high deagglomeration of the particles.