Lung volume, diffusing capacity, chest roentgenogram and dyspnea index in interstitial lung disease.

To investigate the physiologic impairment and the role played by pulmonary function tests in interstitial lung disease (ILD), we performed spirometry tests and tested the single-breath carbon monoxide diffusing capacity of 27 patients with diffuse interstitial pulmonary fibrosis (DIPF) and 35 patients with collagen vascular disease (CVD). All of the patients showed irregular linear opacities on their chest X-ray films. Corresponding chest roentgenograms for each patient were evaluated according to the International Labour Organization (ILO) classification. A modified Baseline Dyspnea Index (BDI), which incorporate a patient's physical activity into the recording, was used to quantitate dyspnea. Patients with DIPF demonstrated a comparable reduction in both lung volumes and diffusing capacity. In contrast, patients with CVD had a greater reduction in diffusing capacity than in forced vital capacity (FVC) and total lung capacity (TLC). There were no significant correlations between the type of linear opacities and the severity of the pulmonary function abnormalities, or between the opacities and the dyspnea in either disease group. The profusion of pulmonary infiltrates also did not affect the lung function except for diffusing capacity in patients with DIPF. However, there was a significant loss of FVC, TLC, forced expiratory volume in one second (FEV1) and diffusing capacity with increasing levels of dyspnea. We conclude that pulmonary function parameters may not be equally affected in DIPF and CVD. Approaches using the ILO classification for analysis of chest roentgenograms provide limited information regarding the functional status of patients. Pulmonary functions are significantly related to the extent of a patient's physical activity, if the severity of dyspnea is evaluated carefully using a quantifiable system.