Pulmonary function impairment in patients with combined pulmonary fibrosis and emphysema with and without airflow obstruction

Abstract

Background

The syndrome of combined pulmonary fibrosis and emphysema (CPFE) is a recently described entity associating upper-lobe emphysema and lower-lobe fibrosis. We sought to evaluate differences in pulmonary function between CPFE patients with and without airflow obstruction.

Subjects and methods

Thirty-one CPFE patients were divided into two groups according to the presence or absence of irreversible airflow obstruction based on spirometry (forced expiratory volume in 1 second/forced vital capacity <70% following inhalation of a β ₂-agonist) as follows: CPFE patients with airflow obstruction (CPFE OB ⁺ group, n=11), and CPFE patients without airflow obstruction (CPFE OB ⁻ group, n=20). Pulmonary function, including respiratory impedance evaluated using impulse oscillometry and dynamic hyperinflation following metronome-paced incremental hyperventilation, was retrospectively analyzed in comparison with that observed in 49 chronic obstructive pulmonary disease (COPD) patients (n=49).

Results

In imaging findings, low-attenuation-area scores on chest high-resolution computed tomography, representing the degree of emphysema, were significantly lower in the CPFE OB ⁻ group than in the CPFE OB ⁺ and COPD groups. In contrast, the severity of pulmonary fibrosis was greater in the CPFE OB ⁻ group than in the CPFE OB ⁺ group. In pulmonary function, lung hyperinflation was not apparent in the CPFE OB ⁻ group. Impairment of diffusion capacity was severe in both the CPFE OB ⁻ and CPFE OB ⁺ groups. Impulse oscillometry showed that respiratory resistance was not apparent in the CPFE OB ⁻ group compared with the COPD group, and that easy collapsibility of small airways during expiration of tidal breath was not apparent in the CPFE OB ⁺ group compared with the COPD group. Dynamic hyperinflation following metronome-paced incremental hyperventilation was significantly greater in the COPD group than in the CPFE OB ⁻ group, and also tended to be greater in the CPFE OB ⁺ group than in the CPFE OB ⁻ group.

Conclusion

The mechanisms underlying impairment of physiological function may differ among CPFE OB ⁺ patients, CPFE OB ⁻ patients, and COPD patients. CPFE is a heterogeneous disease, and may have distinct phenotypes physiologically and radiologically.