A new add-on spacer design concept for dry-powder inhalers

A new add-on spacer design concept for a commercial dry powder inhaler (Turbuhaler®, Astra Pharma Inc., Mississauga, Ontario) is proposed here. Design partial optimization is performed using computational fluid dynamics. The performance of a simplified straight diffuser and a partially optimized geometry are evaluated by measuring the impact of these add-on devices on efficiencies of aerosol deposition in an idealized mouth–throat cast. HPLC and UV spectroscopy techniques are used in the aerosol deposition measurements. Turbuhaler® (terbutaline sulfate, 500 μg) aerosol and an inhalation flow rate of 70 l/min are used for both simplified and partially optimized add-on devices. In addition, monodisperse aerosols for three inertial parameter values, ρpdp2Q(g μm2 s−1), of 6635, 14,700 and 23,430 are used for the partially optimized geometry. Compared to Turbuhaler® alone, the newly developed and partially optimized spacer significantly improved total aerosol delivery distal to the mouth–throat cast by approximately 47% for Turbuhaler® aerosol and 17%, 27% and 107%, respectively, for the above monodisperse aerosols. In contrast, the straight diffuser did not significantly improve delivery distal to the mouth–throat replica.