[Analysis of the mechanism on the formation of configuration of F-V curves with tangent time constant in adult humans].
The tangent time constants at high, mid, low lung volumes (tau t75, tau t50, tau t25) were measured from F-V curves of 258 normal adults aged 20-49. The configurations of F-V curves were classified into the plateau, linear, convex and concave types. In terms of distribution ratio, the convex type increased with age, but the concave type decreased with age. The top of F-V curve was chiefly determined by the length of magnitude of tau t75. The magnitude of tau t75 was the longest for the concave type; its top fell down slowly with the formation of a blant round shape. The magnitude of tau t75 of convex type was the shortest; its top fell down rapidly and formed a peak shape. The mid portion of the curve was determined by the length of tau t50 and the height of V50. The tau t50 was longer and V50 was higher in the plateau and concave types, so that the mid portion fell down slowly to form a plateau or to be concave to the volume axis. While tau t50 was shorter and V50 was lower in the convex and linear types, the mid portion became convex to the volume axis or formed a linear shape. The configuration of the tail was determined by tau t25 and V25. The long tau t25 and high V25 in the plateou type implied the extension of plateau to the low lung volumes. While tau t25 in theother 3 types was shorter. However, V25 was higher in the concave type, thus it made the tail fall down fast and become concave to the volume axis. The V25 was lower in the convex type with the tail convex to the volume axis. The height of V25 in the linear type was between the concave and convex ones with the tail falling in a linear fashion.
Huang
G
G
Department of Physiology, School of Basic Medical Sciences, Chengdu.
Li
J
J
Huang
J
J
D000328:Adult; D000367:Age Factors; D005260:Female; D006801:Humans; D008168:Lung / Q000502:physiology*; D008297:Male; D008449:Maximal Expiratory Flow-Volume Curves; D008875:Middle Aged; D013997:Time Factors