Jolyon P. Mitchell Ph.D, Sara-Lou Bates, Cathy C. Doyle B.Sc, and Mark W. Nagel HB.Sc
Trudell Medical Aerosol Laboratory, London, Canada

VHCs are recommended for use with pressurized metered-dose inhalers (pMDIs), especially with small children whose coordination between pMDI actuation and the onset of inhalation may be poor. We compared the delivery of a bronchodilator (CFC-Ventolin^®, GSK, 90 µg/dose albuterol) via two VHCs (AeroChamber Plusª with medium mask, Monaghan Medical Corp., Plattsburgh, NY, (volume = 149 ml)) and OptiChamber^® Advantage, Respironics^®, Pittsburgh, PA (volume = 218 ml )) (n = 5 devices/group). We measured total emitted dose (TED) and fine particle (< 4.7 mm aerodynamic diameter) dose (FPD) at 4.9 and 12.0 L/min, representing inspiratory flow rates achieved by small children, by means of a low flow Marple-Miller cascade impactor equipped with USP Induction port, following compendial procedures. Each VHC was washed with an ionic detergent, rinsed and drip-dried to minimize the influence of surface electrostatic charge. 5-doses of medication were delivered at 30 s intervals from pre-primed and shaken pMDIs. The induction port and stages of the impactor and the VHC were subsequently assayed for albuterol by HPLC–UV spectrophotometry. Measurements of fine particle dose (FPD – particles < 4.7 mm aerodynamic diameter) and total emitted dose (TED) are summarized in the table. Fine particle fraction (FPF) is the ratio of FPD/TED, expressed as a percentage.

mean ± S.D

As expected, both types of VHC largely eliminated coarse particles, with values of FPF > 96% at either flow rate. However, both TED and FPD from the AeroChamber Plusª VHCs were significantly greater than their equivalent values from the OptiChamber¨ Advantage VHCs (un-paired t-test, p ² 0.41). The larger volume of the OptiChamber¨ Advantage VHCs was not associated with improved delivery, indicating that other considerations such as inhalation valve design as well as internal geometry may be important.

OF-02-017