Performance of a Medical Nebulizer when Testing with a Lung Simulator

TAEWON HAN, Michael Falvo, Gediminas Mainelis, Rutgers, The State University of New Jersey

     Abstract Number: 733
     Working Group: Health-Related Aerosols

Abstract
Medical nebulizers are used to deliver aerosolized drugs and in methacholine challenge testing (MCT), where the constriction caused by methacholine aerosol allows determining bronchial hyperreactivity to a certain concentration of the drug, helping to diagnose asthma. Therefore, it is important to accurately determine the drug aerosolization rate and how that depends on initial liquid volume, drug concentration, and use time; losses inside the nebulizer, i.e., drug remaining on the inner walls of the nebulizer, also play a role in the drug delivery rate. The drug delivery rate is assumed to be a linear function of the aerosolization time. Given the importance of the accurate drug delivery rate in MCT test, we investigated the performance of the commonly used AeroEclipse II BAN nebulizer (Monaghan Medical Corporation, Plattsburgh, NY) as a function of the above parameters using a lung simulator (Michigan Instruments, Grand Rapids, MI) to simulate female and male breathing at 14 of breaths/min and tidal volume of 750 and 900 mL, respectively.

Initial testing showed that the initial drug concentration inside the nebulizer increases with nebulization time, and this factor was taken into account. We found that the nebulizer’s drug delivery rate (mg/min) non-linearly depended on initial solution volume (2-6 mL) and operation time (20 sec-10 min); it was linear regarding the drug concentration (0.0625-16 mg/mL). The loss inside the nebulizer ranged from 0.11 to 0.45 mL, and the initial concentration increased by 7% after 10 min of nebulization. When the drug at 16 mg/ml concentration was used, the average delivery rate was 4.5 mg/min over 10 min, compared to 2.7 mg/min reported by the manufacturer. This difference was even higher for 20-sec nebulization: ~7.7 mg/min vs. the same 2.7 mg/min reported by the manufacturer. The results underscore the paramount importance of testing nebulizer performance.