[Forced mid-expiratory flow rate (FEF 25-75%): a critical analysis of its value in recognizing diseases of the small airways].

A total of 245 patients submitted to lung function test were studied. They were divided in 2 groups: A--FEV1.0/FVC greater than or equal to 75% and B--FEF25-75% less than 75%. These groups were further subdivided according to the age of the patients--subgroup 1 less than or equal to 50 years and subgroup 2 greater than 50 years. Patients with restrictive disorders were not included. The spirometric equipment employed was Hewlett-Packard Inc. Pulmonary Function Analyzer 47402-A. The results were obtained through a digital system and calculated from a graph impressed in a xy register. Results were automatically corrected to BTPS. In each group FVC and FEV1.0 were normal. In group A FVC and FEV1.0 were, respectively: A1-99.63 +/- 13.33 and 101.11 +/- 12.24, A2-97.60 +/- 11.06 and 98.81 +/- 12.18, expressed as percentage of predicted values. In group B the results were: B1-97.61 +/- 13.55% and 81.71 +/- 14.44%; B2-100.28 +/- 13.98% and 83.10 +/- 16.42%. The differences were not statistically significant at 5%. In subgroup A1 X FEV1.0/CVF was 83.41 +/- 5.63% and in subgroup A2, 79.42 +/- 4.23%. Maximum mid-expiratory flow rate was 88.64 +/- 24.39% in subgroup A1 and 65.26 +/- 17.88% in subgroup A2. These differences were statistically significant at 1%. In group B, FEV1.0/FVC was always less than 75%. In subgroup B1 it was 68.24 +/- 10.43% and in B2, 64.90 +/- 10.43% and values for FEF25-75% were 48.13 +/- 16.48% and 42.79 +/- 17.68%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)