Static lung mechanics in patients of progressive systemic sclerosis without obvious pulmonary involvement

Pulmonary fibrosis is a common complication in progressive systemic sclerosis (PSS). Physical examination and/or routine pulmonary function tests can, however, detect only relatively advanced disease. We assessed the utility of static lung pressure-volume analysis in detecting lung involvement in patients of PSS without obvious clinical, radiological or spirographic evidence of pulmonary disease. Static lung volumes were determined and expiratory lung pressure-volume measurements were obtained in 10 patients with PSS, using a computerized whole body plethysmograph. Static pressure-volume data was also subjected to monoexponential analysis. All patients had normal total lung capacity. Three patients had reduced static compliance, of whom one also had reduced value for the shape constant K (calculated from exponential analysis of pressure-volume data). Examination of pressure volume curve showed a pattern consistent with interstitial fibrosis in these patients. We conclude that detailed study of lung mechanics can help identify early pulmonary involvement in patients with PSS.