The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

EVALUATION OF PNEUMATIC NEBULIZERS IN AN UPRIGHT AND ANGLED POSITION. Mike Rejaey, RRT; Dean R. Hess, PhD, RRT, FAARC.

Massachusetts General Hospital and Harvard Medical School, Boston MA.

Background:
Pneumatic jet nebulizers are available from many manufacturers. To our knowledge, there have been no published reports of the effect of nebulizer position on its performance.

Hypothesis:
Albuterol delivery differs among commercially available nebulizers and is affected by nebulizer position.

Methods:
A double-sided test lung (Michigan Instruments; Grand Rapids, MI) was used to simulate spontaneous breathing. One side of the test lung was attached to a ventilator (Puritan-Bennett 7200) and lifted the contralateral side to simulate spontaneous breathing. The lung model simulated breathing at 12 breaths/min, I:E ratio of 1:2 with a sine wave pattern, and tidal volume of 0.5 L. The breathing pattern was confirmed with a pneumotachometer placed at the opening to the lung model. The nebulizer was filled with 4 mL containing 2.5 mg of albuterol and operated at 8 L/min until nebulization was complete. To measure albuterol output from the nebulizer, a Puritan-Bennett D/Flex filter was attached to the mouthpiece. To measure particle size, the inlet of a cascade impactor was placed at the mouthpiece and a bias flow equal to the aspiration rate of the impactor was added between it and the test lung. Nebulizers from 3 manufactures were assessed (n = 3 each): Airlife Misty Max 10™ (Allegiance Healthcare, McGaw Park, IL), Micro Mist® (Hudson, Temecula, CA), and VixOne (Westmed, Lakewood, CO). 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. Nebulizers were evaluated in both an upright (vertical) position and turned 60 degrees to the side.

Results:
There was a significant difference in fine particle mass output of the nebulizers in both the upright (Figure 1) and angled (Figure 2) positions (P < 0.001 in each case). There was a significant decrease in nebulizer output when nebulizers were operated at an angle (P < 0.001). There was a significant interaction effect between nebulizers and nebulizer position (P = 0.003), meaning that operating the nebulizer at an angle affected the performance of some nebulizers more than others.

Conclusions:
Albuterol delivery differs among commercially available nebulizers. The output of the nebulizer may be decreased significantly if the nebulizer is not held in a vertical postion. The impact of these findings on patient outcomes should be confirmed in clinical studies. (Supported, in part, by an unrestricted grant from Cardinal Healthcare).


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