The Exclusion of Restrictive Lung Disease by Spirometric Criteria in Patients with a Reduced Forced Vital Capacity

Reductions in forced vital capacity (EVC) as determined by spirometry may result from restrictive or obstructive disease, either alone or in combination. Restrictive disease is implied when measures of forced expiratory flow are relatively maintained, and obstructive disease is present when flow measurements are disproportionately reduced. In the presence of air flow obstruction, the possibility of concomitant restrictive disease contributing to the reduction in FVC is difficult to assess from spirometry alone. Static lung volumes are usually necessary to establish this diagnosis. We evaluated the FEV1/EVC%o obtained at spirometry compared to its predicted normal value. We found it to be useful in eliminating the need for additional testing in many cases in which the question of mixed obstructive and restrictive disease had been raised. Specifically, in patients with obstructive disease and a reduced FVC, an FEV1/FVC% of less than 81%, of the age-, height-, and sex-matched predicted value largely excluded the possibility that concomitant restrictive disease was also present (p\u3c.05). Higher values had no predictive value