The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

ASSESSMENT OF LARGE AND SMALL VOLUME HOLDING CHAMBER PERFORMANCE WITH HFA-FORMULATED ALBUTEROL.

J.P. Mitchell, PhD^{*}, M.W. Nagel, BSc^{*}, D. Coppolo, RRT^{**}, J.L. Rau PhD. RRT^{***}. ^{*}Trudell Medical Group, London, Canada; ^{**}Monaghan Medical Corporation, Syracuse, NY; ^{***}Cardiopulmonary Care Sciences, Georgia State University, Atlanta, GA.

Introduction: The development of non-CFC propellant formulations for pressurized metered dose inhalers (pMDIs) indicates a need for comparative evaluation of small and large volume holding chambers. Purpose: This study evaluated the respirable and total dose delivered from HFA- albuterol pMDI (Airomir^{TM}. 100 \mug unit dose (3 M Health Care Ltd., UK) in small (145 ml) and large (750 ml) volume holding chambers. Methods: The respirable and total unit doses from three pre-washed AeroChamber(r) with FLOWSIGnal^{TM} valved holding chambers (AC; Monaghan Medical Corp.) and the same number of Volumatic holding chambers (V; Glaxo-Wellcome Inc.) were determined with Airomir^{TM} using an Andersen cascade impactor operated at a continuous flow rate of 28.3 ± 0.5 1/min. One actuation from each of five pre-primed pMDIs was delivered at 30 a intervals into each device, sampling the aerosol with no delay following. Similar measurements were made for the pMDIs alone. The albuterol collected in the impactor was assayed by HPLC. Results: (a) The respirable and total unit doses (n=3 replicates; mean ± 1 SD) from the Airomir^{TM} pMDI alone, the AC and V holding chambers were as follows:

pMDI alone AC V

respirable mass±ISD 46.5±2.7 \mug 74.3±3.5 \mu g 81.4±3.0\mug

total mass ± ISD 97.6 ±5.8 \mu g 77.1±3.6 \mu g 83.8±4.3\mu g

Conclusions: The AC provided a similar respirable dose to the V with Airomir^{TM} (unpaired t-test, p= 0.056). A smaller volume holding chamber is therefore just as effective as a large volume chamber with the new HFA- formulated albuterol. The available dose from both AC and V with Airomir^{TM} was more than 95% respirable (particles < 4.7 \mu m aerodynamic diameter).

Reference: OF-96-201

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