Investigation on the influence of design features on the performance of dry powder inhalers: Spiral channel, mouthpiece dimension, and gas inlet.

As inhaler design is rarely studied but critically important in pulmonary drug delivery, this study investigated the influence of inhaler designs, including a novel spiral channel, mouthpiece dimensions (diameter and length) as well as gas inlet. Experimental dispersion of a carrier-based formulation in conjugation with computational fluid dynamics (CFD) analysis, was performed to determine how the designs affect inhaler performance. Results reveal that inhalers with a narrow spiral channel could effectively increase drug-carrier detachment by introducing high velocity and strong turbulent flow in the mouthpiece, although the drug retention in the device is significantly high. It is also found that reducing mouthpiece diameter and gas inlet size could greatly improve the fine particle dose delivered to the lungs, whereas the mouthpiece length plays a trivial influence on the aerosolization performance. This study contributes toward a better understanding of inhaler designs as relevant to overall inhaler performance, and sheds light on how the designs affect device performance.