Classification of maximal expiratory flow-volume types observed in non-smoking healthy young subjects.

Pulmonary function tests were performed on 234 healthy non-smoking young subjects (189 males and 45 females free from respiratory and allergic symptoms). Maximal expiratory flow-volume (MEFV) curves were visually classified into five MEFV types: Type A, convex or straight flow changes; types B, C, and D, concave-convex-concave flow changes; and type E, sudden flow-fall and accompanying decreased flow rates at lower lung volumes. The reproducibility of MEFV patterns were shown by one way analysis of variance (ANOVA) of MEFV data obtained from 4 groups each consisting of 3-4 males and representing different MEFV types. Distribution of MEFV types was different between males and females; the rate of type A was higher in females than in males and those of types B and E were higher in males than in females. When analyzed in terms of three fractional flow rates, Fr-75, Fr-50, and Fr-25, these values could also be classified into 5 types similarly to the visual MEFV type analysis. It is concluded that MEFV type analysis is useful in assessing health conditions.