Bronchoprovocation test by forced oscillation technique: airway hyperresponsiveness in chronic cough and psychogenic...

By measuring the respiratory resistance (Rrs) with the forced oscillation technique, we evaluated the airway responsiveness to methacholine in four groups of subjects (30 normal, 21 asthmatic, 60 chronic cough, and 30 psychogenic dyspnea subjects). After evaluating the airway responsiveness of normal and asthmatic subjects, four patterns of dose-response curves were found. All of the asthmatic subjects were responders (types III and IV), whereas all but two of the normal subjects were nonresponders (types I and II). The responders had more bronchoconstriction than the nonresponders who presented with a significant decrease in FEV1 after the test. If airway hyperresponsiveness to methacholine was defined as Cmin < or = 12.5 mg/mL, then this test showed 100% sensitivity, 97% specificity, a positive predictive value of 95.5%, and a negative predictive value of 100%. According to these criteria, 18 of 60 (30%) chronic cough subjects and six of 30 (20%) psychogenic dyspnea subjects had airway hyperresponsiveness. We conclude that bronchoprovocation test by the forced oscillation technique is a simple, safe and time-saving tool for measuring airway hyperresponsiveness. We also found that airway hyperresponsiveness is a common finding in subjects with chronic cough, and is also present in some subjects with psychogenic dyspnea.