Lung function in progressive systemic sclerosis is dominated by poorly compliant lungs and stiff airways.

Pulmonary function was investigated in 24 patients with progressive systemic sclerosis. The lung volumes were measured by a body plethysmograph. Bronchial and parenchymal properties were studied by relating pulmonary resistance and lung volume to pulmonary elastic recoil pressure. Pulmonary mechanics and arterial blood gases were studied during graded exercise on a bicycle ergometer. The most fundamental abnormality was a less compliant lung parenchyma together with lowered TLC, VC and ventilatory capacity. A mild intrinsic bronchial obstruction was found, irrespective of smoking habits. In 7 patients, resistance did not, however, increase towards residual volume as it does in normal subjects. This phenomenon is interpreted as stiff airways withstanding compression. Blood gas values at rest, and during work, were remarkably normal. There was no correlation between fibrosis judged from static lung compliance and from chest roentgenograms.