Evaluation of Pressurised Metered Dose Inhaler (pMDI) Plume Spray Force When a Valved Holding Chamber (VHC) is Present: A Proof of Concept Investigation to  Identify Propensity for Premature Inhalation Valve Opening  

Mark W Nagel ¹, Jolyon P. Mitchell² & Jason A Suggett ¹

¹ Trudell Medical International, 725 Third Street, London, Ontario, NV5 5G4, Canada

² Jolyon Mitchell Inhaler Consulting Services Inc., 1154 St. Anthony Road, London, N6H 2R1, Canada

Summary

A proof-of-concept experimental study has been undertaken to quantify the force of the aerosol plume emitted from the same pMDI product (Flovent^Ò-125 HFA-Evohaler^Ò), in combination with VHCs having different inhalation valve types. A sensitive force transducer (0 to 2000 mN) attached to a circular disc-shaped target was mounted perpendicular and on-axis with the horizontally-supported VHC, with its mouthpiece exit plane located 1.0 ± 0.1 mm from the target. The force transducer was initially calibrated by actuating three pMDIs without a VHC, with the mouthpiece exit set 25.0 ± 0.1 mm from the target, confirming that a force of 81.3 ± 6.8-mN was delivered, comparable with previously reported measurements. The following VHCs (n=5 devices/group; 3-replicates/VHC) were subsequently evaluated:

1. antistatic SpaceChamber^Ò (Medical Developments International, Scoresby, Australia)
2. Vortex^Ò (PARI Respiratory Equipment, Midlothian, VA, USA)
3. OptiChamber^Ò Diamond^Ò (Philips-Respironics Inc., Parsippany, NJ, USA)
4. antistatic AeroChamber Plus^Ò Flow-Vu^Ò VHC (Trudell Medical International, London, Canada)

Although the VHCs attenuated the plume pulse by almost an order of magnitude, all add-ons transmitted a detectable force from the inhaler-generated plume pulse via their inhalation valves to reach the target. The peak force measurements (mean ± S.D.) for the antistatic AeroChamber Plus^Ò VHC group (2.0 ± 0.5-mN) were lower than values for the other VHC groups (ranging from 3.7 ± 1.7 to 8.3 ± 2.7-mN), possibly because the toroidal valve deflected much of the incoming energy radially to the chamber walls. This new test method may be useful in VHC development as well as quality control.