The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

OPTIMIZATION OF A PROCEDURE USED TO MEASURE AEROSOL CHARACTERISTICS OF NEBULIZED SOLUTIONS USING A COOLED NEXT GENERATION IMPACTOR.

Ariel Berlinski1,2, Janet B. Hayden1,2; 1Pediatrics, UAMS COM, Little Rock, AR; 2Pediatric Aerosol Research Laboratory at ACHRI, Little Rock, AR

Background: Cooling the Next Generation Impactor (MSP Corporation, Shoreview, MN) (NGI) is recommended to minimize evaporation due to heat transfer from impactor to aerosols when evaluating nebulized solutions [Dennis et al. Cooling the NGI - an approach to size a nebulised aerosol more accurately. Pharmeur Sci Notes. 2008;(1):27-30]. This methodology increases testing time for serial testing procedures. We hypothesize that after an initial prolonged cooling time, experiments could be repeated after shorter re-cooling times without sacrificing accuracy. Methods: 3 units of continuous output (HUDSON RCI UP-DRAFT II® Optineb Nebulizer, Teleflex Medical, Research Triangle Park, NC) (HUDSON) and breath enhanced (PARI LC Plus, PARI Respiratory Equipment Inc., Midlothian, VA) (PARI) nebulizers were operated (6 L/min, central air) with albuterol solution (2.5mg/3mL) into a cooled (4∞C) NGI (internal and external filters) calibrated at 15 L/min. Mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), % particles < 5mm (%< 5), and % particles 1-3mm (P%1-3) were compared with 3 different protocols. Initial cooling of the NGI (90 minutes for all protocols) was followed by 2 measurements with re-cooling intervals of either 90 and 90 (protocol A), 60 and 60 (protocol B) or 30 and 30 minutes (protocol C). Albuterol was diluted and measured by spectrophotometry (276 nm). Aerosol characteristics were calculated using CITDAS 3 software (Copley Scientific, Nottingham, UK). Data were compared using ANOVA for repeated measures. A p < 0.05 was considered statistically significant. Results: MMAD, GSD, P%< 5, and P%1-3 for first measurements of all protocols (n=9) were: 3.47 ± 0.21 mm, 2.31 ± 0.07, 67.3 ± 2.6%. and 40 ± 2.3% (PARI) and 4.56 ± 0.35 mm, 2.16 ± 0.08, 54 ± 3.7%, and 22.4 ± 2.8% (HUDSON). No differences were found between cooling protocols (p > 0.05). Percentage of variation from first measurement ranged from: -3.9 to +2.1% (PARI) and -4.1 to +2.9% (HUDSON) for MMAD; -5.6 to +2.6% (PARI) and -4.9 to +1.9% (HUDSON) for GSD; 0 to +4.6% (PARI) and -3.7% to +5.7% (HUDSON) for P%< 5; and -2.4 to +5.2% (PARI) and -1.8 to +4.9% (HUDSON) for P%1-3. Conclusions: Aerosol characteristics of nebulized solutions determined by NGI are not affected by performing 2 repeat measurements after re-cooling the impactor for either 30 or 60 minutes after an initial 90 minute time. This modification of the procedure increases productivity without losing accuracy. Sponsored Research - None