Design And Analysis Of A Novel Dry Powder Inhaler

In recent years, more and more attentions have been attracted to the development ofdry powder inhalers (DPIs), as DPIs proved to be cost-effective, ease of use,propellant-free and lack the need for patient coordination between actuation andinhalation. While the traditional DPIs are actuated by the inhalation of patients, andtherefore the aerosolisation performance of dry powders is highly restricted to the flowrate of inhalation, which causes the problems of unstable and low delivery efficiencies.In this paper, a novel approach was explored to aerosolize the dry powders in use ofthe mesh with micronized pores. The external power source was employed to generatehigh frequency vibration, in order to improve the dispersibility and aerosolisationperformance of spray-dried powders. These micro-mesh devices were subsequentlytested in use of the spray-dried model drugs, and the ANSYS simulation analysis methodwas utilized to scrutinize internal flow field for the design and optimization of dry powderinhaler device. Based on the optimized data, a prototype of dry powder inhaler wassubsequently manufactured with the piezoelectric transducer as the external powersource.The in-vitro deposition was carried out to determine the effect of this novel drypowder inhaler in manipulating the aerosolisation of spray-dried model drugs. As thedecrease of mesh size from160μm to110μm, the fine particle fraction of loaded(FPFLoaded) drugs was increased from9.44%to11.85%, while the emitted rate had noobvious change and was maintained at about16%. As the high frequency vibrationsource was employed, the emitted dose was dramatically increased from~16%to~80%, and the FPFLoadedwas in the range of26-37%. These phenonmena greatlysuggested the use of high frequency vibration can dramatically improve theaerosolisation and subsequent lung deposition of spray-dried powders. However, the fine particle fraction of emitted (FPFEmitted) drug particles was greatly decreased from75%to50%, which indicated the flow rate and turbulence may be key issues toeffectively improve the aerosolisation and lung deposition of dry powders. In order toproduce the efficient air flow, the Fluent module of ANSYS Workbench was used for thesimulation of flow field inside the dry powder inhaler. A dry powder inhaler withoptimized structure was subsequently designed with tangential inlet and step surface, bywhich the turbulence can be generated, and the turbulent kinetic energy was increased.This dry powder inhaler with optimized structure can effectively reduce the collisionbetween drug particles and the inner wall, which therefore greatly improved theFPFEmittedto75.7%and the FPFLoadedto46.6%. These data clearly demonstrated that thevibrated micro-mesh and the optimized flow channel played a key role to generate asatisfactory aerosolisation performance of spray-dried drug powders for efficientpulmonary delivery. This novel dry powder inhaler with optimized structuredemonstrated much higher delivery efficiency to the lungs than currently marketeddevices, and therefore would have a great potential to be used in clinic.