Wada Y, et al. - Researchers retrospectively reviewed data for stable COPD patients to determine the quantitative computed tomography (CT)-based diversity of respiratory physiology, including the respiratory impedance and reversibility of airway obstruction in patients with COPD. They compared the pulmonary function among the four phenotypes identified based on the degree of emphysema and airway wall thickness: “normal by CT” phenotype, the airway-dominant phenotype, the emphysema-dominant phenotype, and the mixed phenotype. They found that quantitative CT showed a diversity of respiratory physiology, including the respiratory impedance and reversibility of airway obstruction, in COPD patients. The degree of airway disease may be indicated by forced oscillation technique measurements, which may help in the detection of airway remodeling in patients with COPD.