[Evaluation of pulmonary function parameters in twins].

The purpose of this study was to determine the role of genetic influence on the variability of pulmonary function tests in normal individuals. Thirty-one pairs of twins (20 monozygotes (MZ) and 11 dizygotes (DZ) of both sexes, ranging in age from 15 to 18 years, were tested. Degree of similarity in each parameter was compared between MZ pairs and DZ pairs by within-pair variance ratio (MWDZ/MWMZ). The within-pair variances of MZ were smaller than DZ with respect to FVC, FEV1/FVC, V50, V25, delta N2 and FRC. These parameters were corrected for height; again the within-pair variances of MZ were smaller than DZ with respect to all the parameters except for FRC. The results indicate that these parameters were at least partly determined by genetic factor. However the within-pair variance of FEV1, PF, CV/VC, Raw, Pao2, Paco2, pH, and [HCO3-] were not different between the two groups. To estimate the similarity within MZ pairs, among-pair to within-pair variance ratio (MAMZ/MWMZ) were used. All the parameters of pulmonary mechanics showed similarity within pairs. Arterial pH and Pao2 also disclosed a significant similarity within-pairs, but Paco2 and [HCO3-] did not.