The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

LABORATORY EVALUATION OF NEW GENERATION PNEUMATIC NEBULIZERS.

Angeliki Siafaka, MD; Dean R. Hess, PhD, RRT, FAARC, Luca M. Bigatello, MD. Massachusetts General Hospital and Harvard Medical School, Boston MA.

Background:
In recent years, several nebulizer designs have become available in an effort to improve the performance of these devices - primarily by decreasing waste during the expiratory phase. Such designs include bags to collect aerosol during the exhalation phase (Circulaire, Westmed, Engelwood, CO), breath-enhanced designs that increase aerosol output during the inspiratory phase (Pari, Monterey, CA), and breath-actuated designs that produce aerosol only during the inspiratory phase (AeroEclipse, Monaghan, Plattsburgh, NY).

Hypothesis: Albuterol delivery is improved with nebulizers designed to decrease aerosol waste during the expiratory phase.

Methods: A Puritan-Bennett 840 ventilator was attached to one chamber of a dual-chambered test lung. A lift bar was placed between the chambers such that the ventilator triggered simulated spontaneous breathing of the second chamber at a rate of 20/min and a tidal volume of 0.5 L. The nebulizer was filled with 4 mL containing 2.5 mg of albuterol and operated at 8 L/min for 15 min. The nebulizer was operated until nebulization was complete. To measure albuterol output from the nebulizer, a Puritan-Bennett D/Flex filter was placed between the nebulizer and the test lung at the position of the mouthpiece. To measure particle size, the inlet of a cascade impactor was placed at the position of the mouthpiece and a bias flow equal to the aspiration rate of the impactor was added between it and the test lung. The Circulaire, Pari, AeroEclipse, and a conventional pneumatic nebulizer (Micro Mist, Hudson, Temecula, CA) were assessed (n = 3 for each). Albuterol washed from the filter and from the stages of the cascade impactor was measured by UV spectrophometry. Fine particle mass was calculated as the mass of particles with a size <4.7 microns.

Results: There was a significant difference in both the mass output of the nebulizers and the fine particle mass output (P < 0.001 in each case) (Figure 1). Although the output of the breath-actuated nebulizer was greatest, this nebulizer was also associated with a longer nebulization time (P < 0.001) (Figure 2).

Conclusions: Albuterol delivery is greater with the newer generation of pneumatic nebulizers - presumably due to less waste during the expiratory phase. The cost/benefit and impact of these finding on important patient outcomes should be confirmed in clinical studies.

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