Cascade Impactor Study of Aerosolization Process During Passive Dry Powder Inhaler Performance Under Unsteady Versus Steady Flow Conditions

Abstract

The passive Dry Powder Inhalers (DPIs) rely on the human’s inspiratory airflow and negative pressure drop to create turbulent energy environment inside the inhaler. It induces the forces provided by the flow field to fluidize and disperse the drug aggregates into respirable aerosol, exposed to fluid motions. Hence, aerosolization, transport and deposition phenomena with respect to unsteady flow conditions constitute a subject of biomedical research applying methodology of chemical and process engineering. In vitro pharmacopoeia methods - inertial impaction sizing techniques - have been adopted to assess the aerodynamic performance of powder drug-device platforms. The necessity of investigating time-dependent breathing profiles during operation of DPIs renders conventional testing insufficient. Recently, a method using cascade impactor, mixing inlet and breathing simulator has been developed. The hypothesis of the study was proven to be true: the dynamics of the flow conditions influence the aerodynamic particle size distribution of a drug-passive DPI platform. Research efforts focused on mimicking DPI drug delivery with time-varying flow profile may help to develop better in vitro - in vivo correlation (IVIVC) when linking the information gained from compendial testing to clinical efficacy. Further insight of quality parameters in time series is desired to better understand the dynamics of aerosolization process.