Performance of Different Nebulizers for Bronchial Challenge Testing

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

     Abstract Number: 268
     Working Group: Health-Related Aerosols

Abstract
Chronic respiratory health conditions, i.e., asthma, rhinitis, and sinusitis, affect a high number of military personnel , especially Veterans who served in the Southwest Asia theater of operations. At the same time, diagnosing asthma is difficult due to a lack of a gold standard test, and many cases may be misdiagnosed.

Bronchial challenge testing, specifically methacholine challenge testing (MCT), is a mainstay in the assessment of asthma. The constriction caused by MCT aerosol allows determining how “reactive” an individual’s lungs are to a certain concentration of the drug, helping to diagnose asthma. The accuracy of this test depends on the delivered drug dose, which is determined by the breathing time and pattern, drug concentration in a nebulizer, and the nebulizer characteristics. The latter component, however, is rather poorly characterized, leading to uncertainty in the delivery of methacholine and may affect accuracy of the test.

Thus, the goal of this project was to characterize aerosol output from different nebulizers used in the MCT challenge and also test the effects of different breathing patterns on MCT delivery. One of the goals was to determine the PM5 aerosol fraction, i.e., dp < 5 µm in aerodynamic diameter, produced by various nebulizers and different drug concentrations, as this fraction is used by medical personnel to calculate the delivered MCT dose. The examined nebulizers included AeroEclipse II BAN, AeroGen, and MicroMist. The data show that the nebulizer output characteristics, such as total mass and PM5 fraction depend on a nebulizer type, drug concentration (e.g., 0.0625, 0.25, 1, 4, and 16 mg/mL), and breathing pattern (e.g., healthy and asthmatic individual). We also observed that the PM5 fraction varies between 50 and 70%. The obtained data will be used to construct an information sheet for medical professionals administering the MCT challenge.