The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

Improving aerosol delivery in a mechanically ventilated neonatal lung model



Ryan E Grueber, BS, RRT, Mark J. Hamblin, MD, Rajiv Dhand, MD, Division of Pulmonary, Critical Care & Environmental Medicine, University of Missouri, Columbia, Missouri

Background: Clinical application of inhaled therapy in mechanically ventilated neonates is limited by poor efficiency of current drug delivery systems, with pulmonary deposition of <2% of the nominal dose.

Methods: We compared a jet nebulizer with a neonatal adapter kit (MICRO Micromist, Hudson RCI), a metered dose inhaler (MDI; Proventil, Schering) to a vibrating aperture plate nebulizer (Aeroneb Pro, Aerogen, Mountain View, CA). Each device was connected into the inspiratory limb ~ 12 inches from the endotracheal (ET) tube (ID 3.0 mm). In two experiments, the Aeroneb Pro was used with a spacer. The MDI was given via a circuit adapter (Instrumentation Industries). We simulated neonatal ventilation with a Bear Cub ventilator (Viasys Medical) using continuous flow time-cycled, pressure limited ventilation. Delivery of a nominal dose of albuterol (2.5 mg; 5mg/ml) or two puffs (180 µg) by MDI to an absolute filter placed at the end of the ET tube was analyzed by spectrophotometry (290nm). Three tests were performed for each setup.

Results:

Comparison of mean albuterol delivery with various devices
Device Circuit condition Mean albuterol delivery (µg) % Nominal dose
Micromist Dry 12.6 0.5
MDI Dry 3.0 1.7
Aeroneb Dry 226 9.1*
Aeroneb with spacer Dry 473 18.9#
Aeroneb Wet 79.0 3.2
Aeroneb with spacer Wet 100 4.0§

*, p<0.001 vs. MDI and Micromist; #, p<0.001 vs. Aeroneb; §, p>0.05 vs. Aeroneb

Conclusion: The Aeroneb Pro improved albuterol delivery in a model of neonatal ventilation compared to the Micromist nebulizer or MDI. Circuit humidity reduced drug delivery while addition of a spacer to the Aeroneb improved drug delivery in a dry circuit. New aerosol technologies could improve efficiency and the efficacy of inhaled therapies in mechanically ventilated neonates.