Emphysema and interstitial lung disease produce opposing effects on expiratory flow rates and lung volumes on pulmonary function testing. However, both can cause reductions in the diffusing capacity for carbon monoxide (DLCO). Patients with concurrent emphysema and interstitial lung disease can present with normal expiratory flow rates and lung volumes, and a marked reduction in DLCO. In this study, we present a prospective series of ten such patients with interstitial lung disease and emphysema.
Symptomatic patients that presented with an isolated reduction in DLCO were identified prospectively from the respiratory outpatient clinic. The medical records, pulmonary function tests (PFT's) and laboratory tests at diagnosis and during follow up were reviewed. Chest radiograph and chest computed tomography (CT) scans were reviewed by a radiologist.
The patients ranged in age from 50 to 85. PFT's revealed: vital capacity (VC) [94.9 ± 6.5]% of predicted, ratio of forced expiratory flow in one second to forced vital capacity (FEV1/FVC) [0.74 ± 0.04], total lung capacity (TLC) [96.0 ± 6.1]% of predicted, and DLCO [42.4 ± 8.6]% of predicted. Emphysema and interstitial lung disease were confirmed on chest radiographs and CT scans.
Emphysema and interstitial processes occurring simultaneously in the lung can present with normal expiratory flow rates and lung volumes and isolated diffusion abnormalities.
The differential diagnosis of an isolated reduction in diffusing capacity should include co-existing emphysema and interstitial lung disease.
Karen Heathcote, No Financial Disclosure Information; No Product/Research Disclosure Information