Distinctive patterns of pulmonary function change according to baseline lung volume and diffusing capacity

SETTING: Multicentre retrospective study in South Korea.OBJECTIVE: To longitudinally evaluate changes in lung volume and diffusing capacity for carbon monoxide (DLCO) with forced expiratory volume in 1 sec (FEV₁).DESIGN: A total of 155 patients with chronic obstructive pulmonary disease (COPD), whose pulmonary function parameters were measured annually for 5 years, were selected from a prospective cohort in South Korea. A random coefficients model was used to estimate mean annual FEV₁, lung volume parameter and DLCO change rates.RESULTS: Patients were classified into four groups based on baseline DLCO and residual volume/total lung capacity (RV/TLC) measurements. The annual FEV₁ decline rate was greater in patients with low DLCO than in those with normal DLCO, with the greatest decline occurring in patients with low DLCO and normal RV/TLC. RV and RV/TLC declined in patients with high RV/TLC, whereas these increased in patients with normal RV/TLC. DLCO decreased longitudinally in all four groups, with the greatest decline occurring in patients with normal DLCO and normal RV/TLC.CONCLUSIONS: Different subgroups of patients with COPD exhibited distinctive pulmonary function change patterns. Baseline DLCO and RV/TLC may be used as physiological markers to predict long-term changes in pulmonary function.