A comparison of 2 methods of continuous aerosol administration during methacholine challenge testing.
BACKGROUND
Exposure to the bronchoconstricting agent methacholine is a potential hazard to technical staff during methacholine challenge testing, which remains a useful and frequently performed test. There are several methods of performing the test. One of the 2 methods listed in the American Thoracic Society's guidelines is the 2-min tidal-breathing method. The methacholine can be inhaled using one of several methods. The loosely-fitting-mask method is likely to produce more contamination of the local environment than a filtered exhalation system.


METHODS
We tested 2 variations of the tidal-breathing method of measuring the methacholine provocational concentration (PC(20), the dose that produces a 20% decrease in forced expiratory volume in the first second). One involved use of the open-mask technique and the other a T-piece-and-filter system that precluded the release of methacholine-containing droplets into the environment. We performed duplicate methacholine challenge tests with 10 subjects who had a wide range of PC(20). The tests were done in random order, and each subject performed one test using the mask and one using the T-piece/filter system.


RESULTS
With the mask system the geometric mean PC(20) was 4.7 mg/mL, versus 5.1 mg/mL with the T-piece-filter system (p = 0.36). These values are very close and would not be substantially different clinically.


CONCLUSIONS
The 2 methods are equivalent, and the low cost of the products used in the T-piece/filter method makes it suitable for reducing technician exposure to methacholine, using potentially completely disposable components.
Hurst
Thomas S
TS
Division of Respirology, Critical Care and Sleep Medicine, University of Saskatchewan, Royal University Hospital, 103 Hospital Drive, Saskatoon, Saskatchewan S7N 0W8, Canada. thurst@duke.usask.ca
Cockcroft
Donald W
DW
Hannah
Victor D
VD
Davis
Beth E
BE
D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000295:instrumentation / Q000379:methods*; D016085:Bronchoconstrictor Agents; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D014109:Total Lung Capacity
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride