Influence of mouthpiece geometry on the aerosol delivery performance of a dry powder inhaler.

Purpose: To investigate the influence of mouthpiece geometry on the amount of throat deposition and device retention produced using a dry powder inhaler (Aerolizer), along with the subsequent effect on the overall inhaler performance.
Materials and Methods: Computational Fluid Dynamics analysis of the flowfield generated in the Aerolizer with various modified mouthpiece geometries (including cylindrical, conical and oval designs) was used in conjunction with experimental dispersions of mannitol powder using a multi-stage liquid impinger to determine how the overall inhaler performance varied as the mouthpiece geometry was modified.
Results: Geometry of the inhaler mouthpiece had no effect on device retention or the inhaler dispersion performance. In contrast, the mouthpiece geometry strongly affected the amount of throat deposition by controlling the axial component of the exit air flow velocity. The radial motion of the emitted aerosol jet was found to have little effect on throat deposition in representative mouth-throat models. Despite the reduced throat deposition, there was no difference in the overall inhaler performance.
Conclusions: For cases where low throat deposition is a key design parameter, this study demonstrates that the amount of throat deposition can be reduced by making minor modifications to the inhaler mouthpiece design.