Mark Nagel1, Rubina Ali1, Jason A Suggett1 & Jolyon P Mitchell2
1 Trudell Medical International, 725 Baransway Drive, London, Ontario, N65 5G4, Canada
2 Jolyon Mitchell Inhaler Consulting Services Inc., 1154 St. Anthony Rd., London, Ontario, N6H 2R1, Canada
Summary
Inhalation profiles are often used in the clinic to evaluate how the patient interacts with their prescribed dry powder inhaler (DPI). The magnitude of the peak inspiratory flow rate (PIF) achievable is viewed as diagnostically important from the viewpoint of device-patient compatibility. This laboratory-based investigation sought to evaluate an Easyhaler® DPI delivering salbutamol sulphate for aerosol aerodynamic particle size distribution (APSD) using a USP/PhEur induction port located upstream of a Mixing Inlet (MI) and a Next Generation Impactor (NGI). The DPI could therefore be subjected to a range of different inhalation profiles, decreasing PIF from 60 to 50 and then to 40 L/min, mimicking potential use by an asthmatic patient experiencing increasingly severe exacerbations. Total delivered mass (TM) and fine particle mass <4.5 μm aerodynamic diameter (FPM<4.5μm) were each comparable between PIFs of 50 and 60 L/min and between 40 and 50 L/min (paired t-test, p≧0.12. However, FPM<4.5μm. decreased slightly, comparing the outcomes between 40 and 60 L/min (p= 0.03). Fine particle fraction <4.5 μm aerodynamic diameter (FPF<4.5μm) values at all three PIFs were comparable (2-way ANOVA, p≧0.05). Even allowing for an increase of about 1.5 μg, estimated by interpolation of the data from stages 1 and 2, to increase the upper size limit for FPM to the compendially recognized upper limit of 5.0 μm, these measures at each PIF were much lower than their equivalent values delivered by pMDI, where aerosol generation is independent of patient effort.