Standardization of methacholine inhalation challenge by a reservoir method

Standardization of methacholine inhalation challenge (MIC) by a reservoir method was performed at Respiratory Unit, Chulalongkorn Hospital. One hundred subjects, including 20 non-smoking healthy subjects, 20 patients with isolated chronic cough, 20 patients with isolated allergic rhinitis, 20 patients with stable chronic obstructive bronchitis, and 20 patients with mild bronchial asthma, were scheduled to perform the test. The aerosolized methacholine was produced by an atomized nebulizer of the Provocation test I (Pari-Starnberg) and the aerosol was kept in a reservoir bag. It was inhaled by each subject via a slow vital capacity. Increasing concentrations of methacholine (0, 0.5, 1, 5, 10, and 25 mg/ml were used. None of the healthy subjects had increased bronchial hyperresponsiveness (BHR). Sixty percent of patients with chronic cough, 60% of patients with allergic rhinitis, 95% of patients with chronic obstructive bronchitis, and 100% of patients with asthma were found to be positive in the MIC tests. No serious effect from methacholine during and after the tests was found. It was concluded that MIC can be easily performed by a reservoir with reproducible results to demonstrate BHR.