Experimental Evaluations of Internal Losses in ‘Miller’ Mixing Inlet (MI): Part 2 – Dry Powder Inhaler (DPI) Testing for Aerodynamic Particle Size Distribution (APSD)
Svensson M1, Mitchell JP2, Andersson PU3, Parry M4
1 Emmace Consulting AB, Scheelevägen 22, 223 63 Lund, Sweden
2Jolyon Mitchell Inhaler Consulting Services Inc., 1154 St. Anthony Road, London, N6H 2R1, Canada
3 Inhalation Product Development, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83, Mölndal, Sweden
4 Intertek Melbourn, Melbourn, Cambridge, SG8 6DN, UK
Summary
The ‘Miller’ design of mixing inlet (MI) enables a cascade impactor to operate at constant flow rate whilst the inhaler-on-test can be evaluated at varying flow rates. We report an evaluation of the losses within this inlet with three separate evaluations; each evaluation conducted with one or more passive DPIs. A similar evaluation with a pressurised metered dose inhaler and nebulizer was presented at DDL-2022 as Part 1 (Cooper et al.). All evaluations were undertaken with fixed flow rates of compressed air added to the MI to enable a Next Generation Impactor (NGI) to operate at different fixed flow rates without affecting the flow rate from the DPI-on-test. The detailed configurations and test conditions are described in the abstract. Internal MI losses were DPI-dependent, in the worst case, being close to 5%, but more commonly values were in the range from 1 to 4% of the API mass recovered per actuation.