Vishal Chaugule1, Suzanna Olofsson1, Larissa Gomes dos Reis2, David F Fletcher3, Paul M Young2,4, Daniela Traini2,5 & Julio Soria1
1Laboratory for Turbulence Research in Aerospace and Combustion (LTRAC), Department of Mechanical and Aerospace Engineering, Monash University, Clayton Campus, Melbourne, VIC 3800, Australia
2Respiratory Technology, Woolcock Institute of Medical Research, Sydney, NSW 2037, Australia
3School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW 2006, Australia
4Department of Marketing, Macquarie Business School, Macquarie University, NSW 2109, Australia
5Department of Biomedical Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, NSW 2109, Australia
Summary
The time-dependent behaviour of the aerosolized inhalation flow produced from a dry powder inhaler (DPI) significantly affects the dynamics of aerosol generation. A characterisation of such an unsteady DPI flow is therefore important to better understand the device aerosol performance. The unsteady flow emerging from two analogue DPI models, one with and the other without a grid, has been examined. These models are a modified form of an original design with two tangential inlets. Particle image velocimetry was used to measure the spatio-temporal DPI fluid flow velocity field. These measurements were performed using a piston-driven water-based experiment under geometrically and dynamically similar conditions to the original DPI model operating in air, and were taken in a longitudinal plane outside the DPI mouthpiece. The unsteady inhalation flow through the DPI is simulated by a forward piston-stroke pushing fluid through the DPI model. The ensemble-averaged velocity vector-fields for the two models show the spatio-temporal evolution of the emerging DPI flow. An axially-recirculating and laterally-spreading jet flow arising from the model without the grid is found to develop. These flow features occur due to high flow-swirl and lead to drug losses due to particle retention in the device and deposition due to impaction in the mouth-throat region. The jet flow emerging from the model with the grid is found to spread less, but has a large central reverse-flow region that persists for a considerable time of the flow duration.
Key Message
The spatio-temporal evolution of the flow-field emerging from two DPI models outline the formation and growth of axially-recirculating and lateral-spreading flow regions. These affect the device aerosol performance, with the reverse flow leading to drug particle retention in the device, and the lateral-spreading results in impaction losses in the mouth-throat region.