A Comparison of Three Nebulizers for Standard Clinical and Research Use in Methacholine Challenge Testing

Sixty asthmatics (20 at each testing site: University of Saskatchewan, McMaster University, Laval University) will be recruited to undergo this randomized, triple cross-over study. Three nebulizers will be tested, the Wright, the Bennett-Twin and the new Aeroneb Solo.

Breakdown of study procedure: Participants will undergo three (potentially four) methacholine challenges, one with each nebulizer in randomized order. An additional methacholine challenge may be performed for screening purposes if the participant has not undergone methacholine challenge testing in one of the participating labs in the previous 6 months. The screening challenge will be performed with the standard nebulizer used at the given testing site (i.e. the Wright or the Bennett-Twin).

The methacholine challenges performed with the Wright and Bennett-Twin nebulizers will follow the two-minute tidal breathing protocol as outlined in the 1999 American Thoracic Society Guidelines for Methacholine Challenge Testing. The testing protocol used with the Aeroneb solo will be identical save for a 1 min inhalation period instead of 2 min. Each challenge will be stopped when a participant's forced expiratory volume in 1 second (FEV1) drops at least 20%. This will allow for the determination of the participant's PC20 (provocative concentration of methacholine causing a 20% fall in FEV1), which will subsequently be converted to a PD20 (provocative dose) value. A minimum 24-hour washout period between challenges will be enforced.

Inclusion criteria

• Men and women aged 18 or older
• Stable asthma
• Baseline methacholine PC20 less than or equal to 16mg/mL
• Baseline lung function greater than 65% predicted

Exclusion criteria

• Use of long-acting bronchodilators within 30 days of Visit 1
• Pregnant or nursing
• Cardiovascular problems
• Respiratory illness within 4 weeks of Visit 1
• Allergen-induced asthma exacerbation within 4 weeks of Visit 1