Use of forced inspiratory vital capacity to identify bronchodilator reversibility in obstructive lung disease

The objective of this study was to assess the utility of forced inspiratory vital capacity (FIVC) to identify bronchodilator reversibility (BDR) for patients with obstructive lung disease (OLD) in relation to customary BDR criteria as defined by the American Thoracic Society (ATS). Concurrent data analysis was used in an academic medical center setting. Two hundred patients with OLD (including chronic obstructive lung disease and asthma) undergoing testing at the Pulmonary Function Laboratory at Cedars-Sinai Medical Center from January 1995 to December 1996 were identified. These 200 patients were categorized into four grades of obstruction by ATS-defined forced expiratory volume in 1 sec (FEV1) criteria (severe, moderately severe, moderate, and mild). Each of these groups was further subdivided into equal subgroups according to the presence (+) or absence (-) of BDR. Inspiratory flow-volume loops and FIVC were analyzed for each of these subgroups. Of the patients exhibiting BDR on the forced expiratory maneuver (FEM), FIVC correctly identified 53% of the cases. For patients not exhibiting BDR on FEM, FIVC identified an additional 12 cases. In 72% of cases, the maximal FIVC was not obtained from the maximal FEM flow-volume loop. FIVC inspection of the data (which were already available from standard spirometric testing) identified a subgroup of OLD patients with BDR not appreciated by FEV1 or FVC criteria, which may respond to bronchodilator therapy. The maximal FIVC value should be obtained by manual inspection to identify the best inspiratory flow-volume loop.