Genetic Studies on Respiratory Functions by Twin Method

Abstract

Respiratory functions were examined in 56 healthy high school twin students to see the role of genetic factors in determining pulmonary mechanics, lung volumes, gas exchange and ventilatory responses to hypoxia and hypercapnia. Monozygotes (MZ, n=19 pairs) and dizygotes (DZ, n=9 pairs) were matched by age, physical characteristics and sex ratio. MZ and DZ were classified by blood types (ABO, Rh-hr, MN, S, Kell, Lewis, Duffy, Kidd, Lutheran, P, and Xg), fingerprints and facial appearance.
Analysis of covariance disclosed that FVC, FEV₁, and FEV₁% were genetically determined. The role of genetics was not elucidated in FRC, REF, V₅₀, V₂₅, Raw, SGaw, ΔN₂, CV/VC, PaO₂, PaCO₂, pH, and [HCO^-₃]. Ventilatory responses to normocapnic hypoxia and normoxic hypercapnia were also genetically controlled. The effects of smoking were not clearly demonstrated in terms of pulmonary function.
These results suggest that genetic factors are responsible, at least partially, for the variability of respiratory functions seen in normal subjects.