Normal values and evaluation of forced end-expiratory flow.

A new spirometric measurement was performed with 803 healthy, nonsmoking men and women. Using the forced vital capacity curves, the forced end-expiratory flow (FEF75-85%) had a negative correlation with age and a positive correlation with height. Prediction formulas and nomograms were constructed. Comparison with the forced mid-expiratory flow (FEF25-75%) showed generally larger correlation coefficients for physical characteristics and coefficients of variation for the FEF75-85%. Expressing both the FEF75-85% and FEF25-75% as ratios of forced vital capacity did not improve the coefficients. The mean flow rates of 75 male smokers were compared with 213 non-smokers 30 to 49 years of age. The FEF75-85% significantly distinguished between a group of smokers and a group of nonsmokers, but the FEF25-75% showed no significant difference. In 9 patients with presumed peripheral airways disease, FEF25-75% ranged from 70 to 110 per cent of predicted normal but FEF75-85% was 30 to 72 per cent of predicted. An extensively studied control group of 22 healthy, asymptomatic, nonsmoking subjects had FEF75-85% values of 80 to 163 per cent of predicted. Both small groups of 9 patients and 22 control subjects had FEF75-85% values within 1.65 standard error of estimate. In subgroups of 319 persons, use of 75 per cent of predicted mean for FEF75-85% was of greater value in attempting to screen normal from abnormal population than using 1.65 standard error of estimate. The FEF75-85% is suggested as a useful simple ventilatory test to detect early obstructive pulmonary disease.