The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

PERFORMANCE OF FOUR MDI SPACERS, WITH ACTUATION IN PHASE AND OUT OF PHASE WITH INHALATION

Scott A, Foss BS, Joseph N. Lix BA, Jean W. Keppel PhD, David T. Sladek CRTT, Thayer Medical Corporation, Tucson AZ; Paul D. McGowen RRT, Columbia El Dorado Hospital and Thayer Medical Corporation, Tucson AZ

Background: Many users of MDI spacers report difficulty in coordinating actuation of the MDI canister with inhalation. The purpose of this study was to find out how a lack of coordination might affect the amount of medication delivered to the patient's lungs. We tested four hand-held MDI spacers: the Airlife^{TM} Hand Held MediSpacer(R), the Aerosol Cloud Enhancer (ACE(R)), the OptiHaler(R), and the AeroChamber(R). Each brand of spacer was tested under two different conditions: (a) "In Phase," MDI drug canister actuated at the start of inhalation, and (b) "Out of Phase," MDI canister actuated at the start of exhalation. A cascade impactor (analogous to patient's lung) measured particle sizes and dose output at a constant air flow rate, while a breathing machine simultaneously regulated the flow of aerosol medication through a USP standard throat model (analogous to patient's throat). Five different devices of each brand were tested, with Ventolin(R) (albuterol). Method: Output of the spacer travels to the throat model, which feeds into a tee. One branch of the tee feeds into the cascade impactor, with a constant flow rate of 28 L/min maintained by a vacuum pump; the other branch attaches to a wye that has a breathing machine on one branch and a pressurized air source on the other. The air source is adjusted so that the net flow through the throat model = 0 before the breathing machine is turned on. Flow from the air source back through the tee to the vacuum pump bypasses the throat model, so flow through the throat is regulated entirely by the cyclic air flow of the breathing machine. Results: Tabulated below are the averages for µg of drug per dose in the respirable range (1-5 µm) reaching the cascade impactor. Two-tailed t-tests with unequal variances were done; any differences between the averages (for In-Phase and Out-of-Phase) were considered statistically significant if p < 0.05. The p-values are given below. Also given for each device is the ratio of respirable dose In Phase to respirable dose Out of Phase:

MediSpacer ACE OptiHaler AeroChamber

In Phase (µg) 36 ± 3(StdDev) 26 ± 6 15 ± 4 24 ± 2

Out of Phase (µg) 24 ± 6 6 ± 4 1.3 ± 0.3 11 ± 3

p-value 0.005 0.0005 0.002 0.0002

Ratio, In-Phase:

Out-of-Phase 1 : 0.67 1 : 0.23 1 : 0.09 1 : 0.46

Conclusions: For all four brands, the amount of drug delivered to the cascade impactor was significantly less in the Out-of-Phase case as compared with the In-Phase case. This decrease was not due to any change in µg/dose deposited in the throat, as t-tests gave p > 0.05 in the comparison of throat-model washings for the In-Phase and Out-of-Phase cases (all four brands). Instead, washings from the spacers themselves showed that the decrease was due to leakage of drug out of the spacer (MediSpacer and ACE) or increased deposition of drug on the inner walls of the spacer (OptiHaler and AeroChamber). The main inference to be drawn is that, while device design is important, timing greatly affects the amount of drug delivered to the lung by any spacer.

OF-97-048

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