Performance Comparison of Nebulizer Designs: Constant-Output, Breath-Enhanced, and Dosimetric

INTRODUCTION: Design differences among pneumatically powered, small-volume nebulizers affect drug disposition (percentage of the dose delivered to the patient, lost to deposition in the equipment, and lost via exhalation to ambient air) and thus affect drug availability and efficacy.

OBJECTIVE: Evaluate in vitro the dose disposition with 5 nebulizer models, of 3 types (constant-output, breath-enhanced, and dosimetric), using simulated normal, adult breathing.

METHODS: We compared 5 nebulizer models: 2 constant-output (Misty-Neb and SideStream), 1 breath-enhanced (Pari LCD), and 2 dosimetric (Circulaire and AeroEclipse). Each nebulizer was filled with a 3-mL unit-dose of albuterol sulfate and powered by oxygen at 8 L/min. The nebulizers were connected to an induction throat, connected to a breathing simulator. We measured (1) inhaled drug (subdivided into mass deposited in the induction throat and mass deposited in the filter at the distal end of the induction throat), (2) exhaled drug (lost to the ambient air), (3) drug lost to deposition in the apparatus, and (4) drug left in the unit-dose bottle. The duration of nebulization (until sputter) was measured with a stopwatch. All drug amounts were analyzed via spectrophotometry and expressed as a percentage of the total dose.

RESULTS: The mean ± SD inhaled drug percentages were: Misty-Neb 17.2 ± 0.4%, SideStream 15.8 ± 2.8%, Pari LCD 15.2 ± 4.2%, Circulaire 8.7 ± 1.0%, and AeroEclipse 38.7 ± 1.3%. The mean ± SD percentages of drug lost to the ambient air were: Misty-Neb 26.8 ± 0.7%, SideStream 17.3 ± 0.4%, Pari LCD 18.3 ± 0.8%, Circulaire 12.3 ± 0.8%, and AeroEclipse 6.6 ± 3.3%. The mean ± SD percentages of drug lost to deposition in the apparatus were: Misty-Neb 52.3 ± 0.6%, SideStream 63.4 ± 3.0%, Pari LCD 62.5 ± 4.0%, Circulaire 75.8 ± 0.5%, and AeroEclipse 51.0 ± 2.1%. Duration of nebulization was shortest with the Circulaire and longest with the AeroEclipse (p < 0.05 via 1-way analysis of variance).

CONCLUSIONS: The nebulizers we tested differ significantly in overall drug disposition. The dosimetric AeroEclipse provided the largest inhaled drug mass and the lowest loss to ambient air, with the test conditions we used.