[Significance of forced expiratory vital capacity-curves to detect early mechanical alterations in human lungs (author's transl)].

In persons who have been smoking cigarettes for many years, who have normal conventional lung function tests the semilogarithmical plotting of forced expiratory vital capacity curves (FEVC) shows statistically significant differences in volume changes below 25 per cent of vital capacity when compared to FEVC-curves of normal subjects of comparable age. On the basis of the equal pressure point theory it is suggested that the simple semilogarithmical plotting of FEVC-curves may reveal early mechanical alterations rather than can be shown by spirometry and airway resistance measurements.