Acoustic methodology for predicting spray velocity effects on potential lung deposition

Andy Cooper¹, Chris Blatchford¹, Barzin Gavtash²

¹3M Drug Delivery Systems Ltd, Loughborough, Leicestershire LE11 1EP

² Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, LE11 3TU, United Kingdom

The research established acoustic measurements as a potential rapid technique for increasing the efficiency of early phase product development of pMDIs by assisting in lung deposition predictions.

Actuation duration was inferred from the sound duration ascertained via acoustic measurements. For comparison of simple pMDI systems this can yield information on spray velocity, a critical characteristic in terms of lung deposition. Data for spray velocity are also presented. The spray duration trends are compared to those when using numerical modelling of propellant flow inside the pMDI metering valve. Spray duration trends are also compared to in-vitro APSD data, specifically the emitted dose post-throat (%).

The experiments showed that in order to maximise post-throat deposition, the actuator exit orifice should be minimised in order to increase actuation duration / reduce spray velocity. The data also shows that MDIs containing propellant 227 had a longer actuation duration and higher post-throat deposition than MDIs containing propellant 134a. pMDI systems with a reduced actuator exit orifice and propellant 227 may therefore yield increased lung deposition although this combination may not be suitable for all drug formulations.