Lung function values, especially FVC, are preserved in CPFE. This is thought to be the consequence of two counteracting disease patterns: pulmonary fibrosis restricts the lung volumes while emphysema hyperinflates them. The gas exchange, however, is significantly decreased in CPFE patients compared to IPF patients due to the combination of fibrotic and emphysematous lung disease and in some cases also due to PH.
Jankowich MD, Rounds SI. Combined pulmonary fibrosis and emphysema syndrome: a review. Chest. 2012;141(1):222-231.