Usefulness of impulse oscillometry for the assessment of airway hyperresponsiveness in mild-to-moderate adult asthma.

BACKGROUND: Impulse oscillometry (IOS) is a novel method of assessing airway resistance. IOS is rarely used in assessing airway resistance after bronchoprovocation in adult asthma. OBJECTIVE: To ascertain the degree of change in IOS measurements seen in patients with asthma undergoing bronchial challenge testing. METHODS: Patients 18 to 65 years old with mild to moderate asthma, forced expiratory volume in 1 second (FEV1) greater than 80% predicted, and diurnal FEV1 variation less than 30% and taking inhaled corticosteroid (≤1,000 µg/day of beclomethasone dipropionate equivalent dose) were recruited. Sequential spirometry and IOS results were measured during bronchial challenge testing to inhaled methacholine and histamine. RESULTS: The magnitude of percentage of change demonstrated in total airway resistance at 5 Hz was greater than that observed for FEV1 in the 2 bronchial challenge tests. For example, at a methacholine provocation concentration that caused a decrease in FEV1 of 20%, a 43.5% change (95% confidence interval 29.4-57.5) was seen in total airway resistance at 5 Hz as measured by IOS compared with a 23.3% change (95% confidence interval 18.7-27.9) in FEV1. The magnitude of change seen with other IOS outcomes, including peripheral airway resistance, area under the curve, and resonant frequency, also was greater compared with spirometry. CONCLUSION: The potential application of IOS in the assessment of airway hyperresponsiveness in adult asthma has been demonstrated. Further population studies are required. TRIAL REGISTRATION: www.clinicaltrials.gov (NCT01074853).