Should We Measure the FEV1 or the Specific Resistance of the Airways? An Evaluation in Patients with Either COPD, Chronic Dyspnea or Chronic Cough*

Background: The purpose of this study was to evaluate the relative contribution of measuring the forced expiratory volume in one second (FEV1) or the specific resistance of the airways (sRaw) in adults referred for chronic obstructive pulmonary disease (COPD), chronic dyspnea or chronic cough. Methods: This was a prospective study of 321 subjects referred for lung function testing, in a setting of routine clinical management, for suspicion of COPD (or follow-up of known COPD), chronic dyspnea or chronic cough. The proportions of FEV1 values below the normal range and of sRaw values above the normal range were compared using a Chi-square exact test of Fisher. Results: In the COPD and chronic dyspnea groups, sRaw was as frequently abnormal as FEV1. In the chronic cough group, sRaw was increased in 56.5 % of subjects, while FEV1 was decreased in solely 34.8 % (p = 0.059). Conclusions: This study suggests that sRaw may be a better tool than FEV1 to detect bronchial obstruction in patients presenting with chronic cough