Purpose: The DPI device plays a key role in the dispersion of DPI formulations into fine particles. The dispersion patterns of inhaled particles depend not only on the powder formulation but also on the design of the inhaler device. More specifically, design of the mouthpiece could have a direct impact on the fluid dynamics properties of the particles exiting the inhaler device. In this study, four mouthpieces were designed and constructed in a computer-aided design/computer-aided manufacturing environment (CAD/CAM) with cylindrical, spiral, radial and chamber type and simulated aerosol by computational fluid dynamics.
Methods: The geometries of four mouthpieces were constructed in a CAD/CAM environment (Rhinoceros 5, McNeel North America, Seattle, WA, USA) Computational fluid dynamics was used to numerically analyze the airflow and particle dispersion following emission from non-spiral and spiral mouthpieces of the devices. Aerosol flow rates at 28.3, 60, 90 L/min were simulated for all prototypes. The convergence criterion was that all residuals except for continuity were below 1e-4, and all evaluations were interpreted as steady state.
Results: As a result, the velocity and direction of the different aerosols according to the design of the mouthpiece were shown. To describe the main differences in the mouthpiece design, first, the cylindrical mouthpiece has a lager velocity difference according to the position even at the same flow rate. A turbulent was generated along the side wall. In the case of a spiral mouthpiece, it types a turbulent that rotates along a spiral structure, as well as relatively uniform velocity distribution. The radial mouthpiece moves from the center to the front and aerosols returning to the side were observed, and the flow rate was slow. Finally, the chamber mouthpiece has a lager turbulent and no air flow through the center of the turbulent. The important difference was the direction of turbulent and flow rate of change in inhaler device. This turbulent not only facilitates impaction in the DPI composed of fine particles, but also helps to disperse the aggregated fine particles. It is confirmed that the design of the mouthpiece is an important factor for the generation of turbulent flow and other aerosol behaviors.
Conclusion: The delivery efficiency to the lungs of the dry powder inhaler is influenced by the physicochemical properties of the particles as well as the inhaler device design. The design of the mouthpiece could have a direct impact on the fluid dynamics properties of the particles emitting the inhaler device.
Jae-Gon Song– Student, Chungbuk National University, cheongju-si, Ch'ungch'ong-bukto
Dong-Wook Kim– Cheongju University, cheongju-si, Cholla-bukto
Chun-Woong Park– Chungbuk National University, cheongju-si, Ch'ungch'ong-bukto