Comparative CFD study on regional drug deposition of Breezhaler® and Handihaler® in the human respiratory tract

Inhalation therapy has become a cornerstone in the management of chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD) and asthma. Among various devices, Breezhaler® and Handihaler® are two widely used dry powder inhalers (DPIs) in clinical practice. However, due to differences in structural design and aerodynamic characteristics, these devices exhibit markedly different drug deposition patterns within the respiratory tract. Currently, there is a lack of comprehensive comparative studies investigating their deposition efficiency and underlying mechanisms across distinct regions of the airway. To address this gap, the present study employs CFD-DPM approach to evaluate and compare the deposition and distribution behavior of Breezhaler® and Handihaler® in the MT, TB, and deep lung regions under five pressure drop levels and four particle size conditions. The results indicate that Breezhaler® features a more streamlined internal structure, allowing the airflow to maintain higher and more uniform velocities. In contrast, Handihaler® generates lower overall airflow speeds and exhibits greater velocity gradients and localized turbulence within the oral cavity. For both devices, oral deposition rates increase with rising pressure drops and particle sizes, with Handihaler® consistently showing higher oral deposition, particularly under elevated flow and particle size conditions. In the TB region, Breezhaler® demonstrates superior deposition efficiency compared to Handihaler®. Enhancing TB deposition with Breezhaler® can be achieved by utilizing smaller particle sizes, while Handihaler® can improve TB deposition efficiency even with larger particles by operating under lower pressure drops. Furthermore, Handihaler® shows better performance in drug delivery to the deep lung region.