The Science Journal of the American Association for Respiratory Care

1999 OPEN FORUM Abstracts

POLYMER VS METAL HOLDING CHAMBERS FOR YOUNG CHILDREN

Bert C. Kesser, Jolyon P. Mitchell, Mark W. Nagel, David E. Geller. The Nemours Children's Clinic, Orlando, FL, and Trudell Medical Aerosol Laboratory, London, ONT.

Background: A valved holding chamber (VHC) with mask allows a young child to use metered dose inhalers (MDI). Small children using tidal breathing often don't begin inhaling at the time of MDI actuation. A non-static metal VHC theoretically increases the dose of drug to the patient by decreasing impaction and increasing dwell time in the device for poorly coordinated breaths. However, the advantages of seeing through the VHC are lost. We compared the in vitro performance of a 230 ml. metal VHC to a prototype 155 ml. transparent polymer VHC for the delivery of budesonide by MDI. A 2-second delay between MDI actuation and aerosol sampling was used to mimic uncoordinated breaths.

Methods: Particle size measurements were made with a Marple-Miller cascade impactor at 4.9 l/min, similar to inspiratory flow rates seen in small children. Each VHC was washed in detergent and dried. A budesonide MDI (200 mg/dose) was shaken, primed, and inserted into the VHC adapter. The MDI was actuated, and 2 seconds later the VHC mask was connected to the USP induction port of the cascade impactor. Five doses were delivered to the impactor in this fashion for each VHC, and 5 VHC's of each type were studied. The stages of the impactor and the VHC were then assayed for budesonide by HPLC.

Mass (mg) <3.1 mm Mass (mg) <4.7 mm Mass (mg) >4.7 mm Total Dose (mg) Retained Dose (mg)
Polymer VHC 11.3 +/- 1.5 32.6 +/- 2.9 12.9 45.5 +/- 5.3 118.2 +/- 18.5
Metal VHC 9.4 +/- 1.2 32.5 +/- 1.4 30.9 63.4 +/- 5.0 110.3 +/- 6.4

Discussion: The dose retained in the VHCs were similar (55-60% of MDI dose). Although the metal VHC allowed more total drug to escape the device, the fine particle mass (FPM=mass of drug < 4.7 mm aerodynamic diameter), which is related to the amount of drug likely to deposit in the lower airways, was equivalent between polymer and metal devices (p=0.95). The polymer VHC filtered the coarse particles (> 4.7 mm) better than the metal VHC. Coarse particles are more likely to impact in the upper airway, and have the potential to cause side effects. Conclusion: Under conditions likely to occur with young children, the prototype transparent polymer VHC delivered equal FPM and was superior to the metal VHC at eliminating coarse particles from a budesonide MDI. Aerosol devices should always be tested under conditions that simulate clinical use.

OF-99-238

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