Pulmonary involvement in patients with rheumatoid arthritis.

Vital capacity (VC) and single-breath diffusing capacity for carbon monoxide of the lungs (Dco) were measured and chest X-ray evaluated in 129 patients with rheumatoid arthritis (RA). 123 of them represented average RA patients, either hospitalized (84 patients, Group I) or outpatient material (39 patients, Group II). The remaining six patients (Group III) represented cases with marked changes in chest X-ray detected in an earlier study. Deviating findings in the 123 cases of Groups I and II were observed as follows: in one the lung function tests or X-ray examinations, 35%; abnormal X-rays, 18%; reduced VC or Dco, 28%; simultaneously low VC and Dco, 7%; and pathological findings in all three tests, 2%. Group III showed extremely low VC and Dco values. Changes in respiratory function involved restrictive impairment and diffusion defects, and the results further implied that restrictive changes develop early, whereas decreased diffusing capacity is associated with more advanced "rheumatoid lung". The disparity abnormal findings in chest X-ray changes and in lung function tests suggests that in examining pulmonary manifestations in patients witu RA, both radiographic methods and pulmonary function tests should be used for relevant evaluation.