Flow Rate-Rise Time Profiles from Model Dry Powder Inhaler (DPI) Testing of Abbreviated Impactor Systems Compared with Their Full Resolution Counterparts: Initial Experimental Data
Mitchell JP1, Roberts DL2, Versteeg H3, Cooper A4, Copley M5 & Greguletz R6
1 Jolyon Mitchell Inhaler Consulting Services Inc., 1154 St. Anthony Road, London, N6H 2R1, Canada
2 Applied Particle Principles LLC, 17347 Westham Estates Court, Hamilton, VA 20158, USA
3 Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, LE11 3TU, UK.
4 Kindeva Drug Delivery, Derby Road, Loughborough, LE11 5SF, UK
5 Copley Scientific Ltd., Colwick Quays Business Park, Rd. No 2, Colwick, Nottingham NG4 2JY, UK
6 Sofotec GmbH, a member of the AstraZeneca Group, Benzstraße 1-3, Bad Homburg, D-61352, Germany
Summary
We report the outcome of a European Pharmaceutical Aerosol Group study evaluating flow rate-rise times for reduced Next Generation Impactor (rNGI), Fast-Screening Impactor (FSI) and Fast-Screening Andersen impactor (FSA) with surrogate low-, medium- and high-resistance DPIs. Time for the flow rate to reach 90% of target (t90) and flow acceleration rate (slopet20/t80) defined the profiles. Volumes of the abbreviated impactors were estimated (±10mL) and compared to published values for their counterpart parent impactors (rNGI and FSI to NGI; FSA to Andersen Cascade Impactor (ACI)). t90 (n=3 replicates; mean±S.D.) for rNGI (system volume 1990 mL, participant D) for target flow rates of 30 and 60 L/min were 387±5 and 218±8 ms respectively, close to corresponding values of 400±7 and 219±6 ms for the NGI (2000 mL). The slopet20/t80) values were 0.09±0.00 and 0.31±0.00 L/min/ms at 30 and 60 L/min for the rNGI, also similar to the NGI value. Values of t90 (170±5; 76±2 ms) and slopet20/t80 (0.22±0.01; 0.96±0.01 L/min/ms) with the smaller FSI (1150 mL), were significantly different at 30 and 60 L/min respectively than those of the NGI. Data from Participant G contained similar divergences including tests at 90 L/min (t90 60±3 ms (FSI); 185±6 ms (NGI). When testing two FSAs (volume of 630 mL) at 60 L/min, Participant J found almost identical t90 values (70±3; 71±2 ms), shorter than 60-L/min values (151±3; 162±6 ms) for their two ACIs (larger volume, 1180 ml). Apparatus internal volume is an important determinant of flow rate-rise time.
Key Message
Our study has identified that the FSI and FSA abbreviated impactors start up more quickly than their parent apparatuses whereas the rNGI starts up nearly at the same rate as the NGI. Apparatus internal volume is an important determinant of the flow rate-rise time profile.