Investigation of dry powder inhaler (DPI) resistance and aerosol dispersion timing on emitted aerosol aerodynamic particle sizing by multistage cascade impactor when sampled volume is reduced from compendial value of 4 L.

Compendial methods determining dry powder inhaler (DPI)-emitted aerosol aerodynamic particle size distribution (APSD) collect a 4-L air sample containing the aerosol bolus, where the flow, which propagates through the cascade impactor (CI) measurement system from the vacuum source, is used to actuate the inhaler. A previous article described outcomes with two CIs (Andersen eight-stage cascade impactor (ACI) and Next-Generation Pharmaceutical Impactor (NGI)) when the air sample volume was ≤4 L with moderate-resistance DPIs. This article extends that work, examining the hypothesis that DPI flow resistance may be a factor in determining outcomes.

Effect of sampling volume on dry powder inhaler (DPI)-emitted aerosol aerodynamic particle size distributions (APSDs) measured by the Next-Generation Pharmaceutical Impactor (NGI) and the Andersen eight-stage cascade impactor (ACI).

Current pharmacopeial methods for testing dry powder inhalers (DPIs) require that 4.0 L be drawn through the inhaler to quantify aerodynamic particle size distribution of "inhaled" particles. This volume comfortably exceeds the internal dead volume of the Andersen eight-stage cascade impactor (ACI) and Next Generation pharmaceutical Impactor (NGI) as designated multistage cascade impactors.