2004 OPEN FORUM Abstracts
COMPARISON OF AEROSOL MEDICATION DELIVERY USING DIFFERENT LENGTH EXPIRATORY RESERVOIRS
Ruben
D Restrepo MD RRT, Douglas S Gardenhire MS RRT, Arzu Ari MS RRT,
Joseph L Rau PhD RRT . Department of Cardiopulmonary Care Sciences.
Georgia State University. Atlanta, GA.
Background:
Most hand-held nebulizers that provide constant aerosol generation
during inspiration and expiration have a T-piece that fits on top of
the unit to allow attachment of a mouthpiece. An optional 6-inch
corrugated tube extension is usually placed at the distal end of the
T-piece (expiratory reservoir). There is no report in the literature
on the impact of using different expiratory reservoir tubing lengths
on the amount of drug available for inhalation.
Objective: To
measure the effect of expiratory tubing of various lengths on the
inhaled dose of a constant output nebulizer.
Methods: An in
vitro model was used to evaluate delivery of nebulized bronchodilator
to simulated spontaneously breathing adults. The Airlife Misty-Neb
was the nebulizer used as it represents an example of a traditional
constant output nebulizer. Eight trials of three system
configurations were run: a nebulizer with T-piece adapter without an
expiratory reservoir; a 6-inch (50 mL) length of large-bore
corrugated tubing attached to the expiratory outlet of the T-piece,
and a 12-inch (100 mL) expiratory reservoir. The amount of aerosol
drug in the filter that was attached to the proximal end of the
T-piece, between the nebulizer and the breathing simulator, was used
as an indicator of the amount of drug available to the patient on
each inspiration. Drug amounts collected at the filter were expressed
as a percent of the nominal dose.
Measurement of Drug: All
drug amounts were analyzed using a spectrophotometer at a wavelength
of 276 nm.
Data Analysis: Means and standard deviations were
calculated for each series measured. Differences across
configurations were compared using repeated measures ANOVA. Pairwise
comparisons were used to identify differences between configurations
at a 0.05 level of significance.
Results: As illustrated in
the bar graph, there was only a significant difference in the amount
of drug measured at the inspiratory filter between the configuration
with no reservoir and the 12 inch reservoir (p= 0.01).
Conclusion:
Attachment of a 12-inch reservoir to the T-piece used with small
volume nebulizers may improve the clinical response to aerosolized
medications. However, pulmonary function testing before and after
aerosol delivery with this configuration, as well as quantification
of carbon dioxide rebreathing from a longer expiratory reservoir
should be evaluated before the results of this study are extrapolated
to clinical practice.