2-Minute Tidal Breathing Methacholine Bronchial Challenge: Comparison of Two Jet Nebulizers.

BACKGROUND The American Thoracic Society (ATS) guideline for methacholine challenge testing (MCT) recommended using the English Wright (EW) nebulizer. However, other brands of nebulizers are also indicated to be acceptable for this technique, but further validation of nebulizer performance is recommended. OBJECTIVE To compare the methacholine provocation concentration causing a 20% fall in forced expiratory volume in 1 second (PC20 -FEV1 ) measured by using EW nebulizer and DV 646 nebulizer. METHODS Subjects were randomly assigned to undergo 2-minute tidal breathing methacholine challenge with either EW or DV 646 nebulizer on two separate days, which were at least 24 hours but not more than 7 days apart. The above procedure was repeated for each subject in one month, but the nebulizers were selected in a reverse order. RESULTS 15 mild and stable asthma patients finished this study. The geometric means (SD) of methacholine PC20 measured with using EW and DV 646 nebulizers were 1.82 (6.38) mg/ml versus 0.83 (1.82) mg/ml, respectively in the initial two visits and 2.56 (6.29) mg/ml versus 0.78 (1.40) mg/ml in the following two visits in asthma (both P < 0.05). There are well correlations between PC20-EW1 and PC20-EW2 (r=0.99, p<0.01), PC20-DV1 and PC20-DV2 (r=0.88, p<0.01), and between PC20-EW1 and PC20-DV1 (r=0.91, p<0.01), PC20-EW2 and logPC20-DV2 (r=0.78, p<0.01). CONCLUSIONS PC20 -FEV1 measured by using the two conventional jet nebulizers was both repeatable and the results were highly correlated.