Combined pulmonary fibrosis and emphysema (CPFE) is a unique disorder that has been previously described, and the distinct features of CPFE in comparison with chronic obstructive pulmonary disease (COPD) have been reported. However, the yearly dynamics of pulmonary function parameters in CPFE patients compared with those in COPD patients have not yet been reported.

We retrospectively enrolled patients with CPFE and COPD who had undergone pulmonary function tests more than five times during a follow-up period of more than five years. The baseline clinical characteristics and the annual changes in pulmonary function during the follow-up period in 16 stable CPFE patients were compared with those in 19 stable COPD patients. Annual changes in pulmonary function were estimated from linear regressions, with assumptions for time-dependency and linearity. We analyzed the time-dependent fluctuations in pulmonary function for the two disorders.

Annual decreases in VC and FVC in the CPFE group were significantly higher than those in the COPD group. Annual decrease in FEV₁/FVC in the COPD group was significantly higher than in the CPFE group. During the follow-up period, FEV₁/FVC in the CPFE group appeared to improve because of annual decrease in FVC. Annual decreases in DLco and DLco/VA in the CPFE group were significantly higher than those in the COPD group.

This is the first report showing the yearly dynamics of pulmonary function parameters in CPFE patients compared with those in COPD patients during a follow-up period of more than five years. This study revealed that the physiologic consequences of CPFE including the rate of progression of pulmonary function impairment were different from those of COPD.