We studied pulmonary functions in 17 female patients with mixed connective tissue disease (MCTD) to detect early pulmonary involvement in this disease; in 8 of the 17 patients follow-up studies were also performed at 1.2- to 5.9-year intervals. In the first pulmonary function tests, decreases in vital capacity (VC) and diffusing capacity (DLCO) were observed in 6 (35%) and 8 (47%) patients, respectively. The ratio of forced expiratory volume in one second to VC was normal in all the patients, but pulmonary resistance and static compliance were abnormal in 6 (35%) and 10 (59%) patients, respectively. However, frequency dependence of dynamic compliance was found in all 16 patients tested. Moreover, 4 (24%) of the 17 patients had normal DLCO and DLCO-to-alveolar volume ratio (DLCO/VA). Reductions in DLCO and DLCO/VA were significantly correlated with the disease duration. These results suggest that small airway obstruction is an early and frequent indication of functional pulmonary impairment, and that impairment of alveolar gas exchange is progressive in patients with MCTD.
- connective tissue disease
- diffusing capacity
- frequency dependence of dynamic compliance
- small airways
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)