The Science Journal of the American Association for Respiratory Care
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
|Mass ( ||Mass ( ||Mass ( ||Total Dose ( ||Retained Dose ( |
|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