Rationale: The American Thoracic Society guidelines for methacholine testing for the diagnosis of asthma recommends the 2-minute tidal breathing protocol with the Wright nebulizer, which produces more aerosol than required, generates a small particle size, and requires cleaning between tests.
Objectives: To evaluate methacholine testing using a disposable, breath-actuated AeroEclipse II, which produces aerosol during inspiration and was developed for single-patient use.
Methods: Forty-six adult subjects with asthma (19 men), aged 27.3 (SD, 9.5) years, with FEV1 98.5 (SD, 18.1) % predicted participated in a randomized, crossover, observational study. Subjects were first screened using the Wright nebulizer, then assigned to 2 minutes of tidal breathing from the Wright or 20 seconds of tidal breathing from the AeroEclipse nebulizer on 2 separate days, in random order. Provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) values were calculated by linear interpolation of log dose-versus-response curves, log-transformed, and compared using paired Student t test and Pearson correlation.
Measurements and main results: The 38 subjects demonstrating reproducible PC20 measurements of within 1.5 doubling concentrations were included in the comparison. The geometric mean methacholine PC20 measured with the AeroEclipse nebulizer was approximately 1 doubling concentration lower than the geometric mean methacholine PC20 of the Wright nebulizer (P < 0.05). The Pearson correlation coefficient between the two nebulizers was 0.86 (P < 0.05).
Conclusions: The PC20 measurements using the two nebulizers were highly correlated; however, the PC20 determined with the AeroEclipse nebulizer was significantly lower than those determined using the Wright nebulizer. Clinical trial registered with www.clinicaltrials.gov (NCT 01919424).
Trial registration: ClinicalTrials.gov NCT01919424.
Keywords: airway hyperresponsiveness; asthma; nebulizer.