Developing alternative delivery systems for methacholine challenge tests.
The two American Thoracic Society recommended aerosol delivery devices for methacholine challenge testing are both obsolete and often very difficult to acquire, leading to the test being done with a number of nonstandardized nebulizers. Of the two recommended devices, one is the English Wright nebulizer used in the 2-min tidal breathing method, and the other is the DeVilbiss 646 nebulizer used in the five-breath dosimeter method. The purpose of this study was to evaluate the in vitro performance of potential alternative devices that would be economically viable and would minimize environmental contamination. One device was the disposable breath-actuated AeroEclipse(®) II BAN as a potential delivery system for the 2-min tidal breathing, and the second was the automated system by VIASYS as an alternative to either the 2-min tidal breathing or the five-breath dosimeter method. A breath simulator mimicked an adult or small child breathing pattern, and a slow inhalation for the five-breath method was generated by a spirometry calibration syringe. Methacholine (Provocholine™) was eluted from filters at the "mouth" and assayed by high-pressure liquid chromatography. In 12 sec, the AeroEclipse II BAN would be expected to have a pulmonary deposition equivalent to the 2-min tidal breathing with the English Wright, whereas the VIASYS system would take approximately 40 sec for the equivalent delivery. The per-breath delivery of the VIASYS and the DeVilbiss 646 was approximately the same, whereas one breath from the AeroEclipse II BAN was the equivalent of five from the DeVilbiss 646. These data will allow for planning in vivo studies to develop methacholine challenge protocols using modern aerosol delivery systems.