Interpretation of manual actuation profiles from nasal unit-dose spray devices

Benedicte Grosjean¹, Gerallt Williams¹, Fabien Adam¹, David Chopard¹, Pierre Schwartz¹, Janick Cabiddu¹

¹Aptar Pharma, Route des Falaises, Le Vaudreuil, 27100, France

Summary

There has been increasing interest lately in Human Factors studies and these are becoming a critical part of aerosol product development. In this case study, a panel of ten volunteers each actuated six unit-dose devices filled with water. The displacement and force over time during the actuation were recorded. The data were analysed to understand qualitatively the curves with regard to the mechanical events that occur to deliver a spray. Two phases could be observed. A first one was very fast, a second one was much slower, during which the liquid enters narrow sections of the flow path within the device and the spray is emitted. The curves did not show neither constant force nor constant velocity as is obtained with an automated machine. However, the second phase would be the one to consider in order to define parameters that would impact the spray performance. Several critical output parameters, like the force to trigger the device, the delivery force, the velocities and the stroke length, were qualitatively analysed. The force to trigger the device and the stroke length were found to be very reproducible (less than 5%) while the delivery force and velocities were quite variable (around 20%). The former are governed by mechanical features in the device, while the latter depend strongly on the specific energy the user applies during actuation. The range of parameters can be used to define suitable levels for automated in vitro tests or for quality control tests.