Interindividual variability of the configuration of maximal expiratory flow-volume curves in normal human subjects

Abstract

Interiiidividiial variability of the configuration of maximal expiratoiy flow–volume curves (MEFV curves) was investigated in 2009 men and 1910 women aged 20 to 70 years. Three configuration types of MEFV curves were separated by means of quality analysis of the curves: “linear”, “convex", and “concave” into the volume axis. Three forms were separated in the “convex” type: spherical, trapezideous and trapezideous with concavation in the last 14 of FVC. The “concave” curves differed on the bend degree (into the volume axis side): the bend in the last 1/4 of FVC, moderate concavation of the whole curve, and extreme concavation which is close to those in patients with impairments  fairways. “Convex” forms were found in 23% of examined normals, “linear” ones were found in 15% of normals, “concave” ones were found in 41% of normals. “Pathologic-bent” curves were found in 11% of nonnal subjects. Volumic (FVC, FEV₁), flow (PEF, MEF₅₀, MEF₇₅, MEF_25-75), and time (MTT and TFVC) parameters were respective to curve forms that are mentioned above. FVC, FEV₁, MEF₅₀, and MEF₇₅ were greater in cases of “convex” forms and were decreased parallelly to curve concavation increase. On the contrary, MTT and TFVC were greater in groups with “concave” fonns of curves and increased parallelly to the concavation increase. It was found, that “concave” curves are featureous for humans which are older than 40 years. Cases of the “pathological–bent” curve did not depend on smoking. The more often cases of the “concave” curve form in humans over 50 years old allow to explaine formation of various flow–volume curves with age changes in airways and pulmonary tissue. The “concave” flow–volume curve fonns obtained in 52% of the examined did not allow to discuss them simply as a qualitative diagnostic sign of pathology in mechanical properties of lungs.