1995 OPEN FORUM Abstracts
Effect of Multiple MDI Actuations on Dose Availability from a Spacer.
J. L. Rau, Ph.D., RRT, Georgia State University, Ruben D. Restrepo, M.D., RRT, Egleston Children's Hospital of Emory University, Vijay Deshpande, M.S., RRT, Georgia State University, Atlanta, GA.
Differences in inhalation technique with reservoir or spacer devices mav affect MDI dose availability to a patient. Purpose: This study examined the effect of single versus multiple actuations of a metered dose inhaler (MDI) into reservoir devices on dose delivery of albuterol, with three clinically available reservoir brands.
Methods: One side of a dual-chambered test lung, whose other side was powered by an MA-2, simulated inspiration from the MDI-reservoir system. Albuterol (Proventil, Schering) was delivered by MDI, with the Monaghan Aerochamber, the DHD ACE, and the Schering InspirEase, using standardized volumes and inspiratory flows of 30 Lpm. Six samples of each brand were tested. The MDI was actuated into each brand of reservoir one, two or three times in rapid succession (two seconsds apart), followed by a single inhalation. Aerosol dose at the reservoir mouthpiece was captured on a cotton filter, dissolved in ethanol and measured with a spectrophotometer at 278 nm. Reservoir dose availability is reported as a percent of the dose obtained directly from one MDI actuation with no reservoir attached.
Results: The Aerochamber, ACE and InspirEase delivered a mean ± SD of 22.3% ± 9.7%, 22.7% ± 4.98%, and 11.6% ± 5.3% respectively with one actuation, compared to 41.2% ± 10.3%, 38.1% ± 10.0% and 18.5% ± 8.1% cumulative does with two actuations, followed by a breath. Paired t-tests indicated that two puffs increased the cumulative dose significantly for each brand compared to one puff (p = .002, p= .024, & p = .004 respectively). The use of three actuations did not significantly increase the amount of drug at the mouthpiece of the reservoir compared to two actuations, using a paired t-test for each brand (p = .8914, p = .058, & p = .077 respectively). There was no significant difference between the Aerochamber and the ACE in dose availability with one, two or three actuations (p = .814), but both of these brands provided significantly more drug than the InspirEase, when tested with a split-plot repeated measures ANOVA (p = .0022 & p = .0027 respectively). Conclusion: Maximal aerosol bronchodilator from a MDI-reservoir was given by single actuations each followed by a breath. Two rapid actuations followed by a breath will give a significant accumulation of dose with minimal loss compared to two single actuations each followed by inhalation. Three multiple actuations are not recommended.