Lung function tests in connective tissue diseases associated with Raynaud's phenomenon.
13 patients with various connective tissue diseases associated with Raynaud's phenomenon were studied with pulmonary physiologic techniques to see the alterations of lung functions and also whether spasm of pulmonary circulation occurs in these patients. We found that an increase in the dead space ventilation was common and associated with normal tidal volume. We interpreted this finding as evidence of redistribution of blood flow in the lung by spasm of blood vessels going to well-ventilated lung units generating a high dead space ventilation. We also found commonly that the distribution of inspired air in the lung was uneven, the diffusing capacity was reduced and the dynamic compliance decreased with increasing frequency of breathing suggestive of disease in small airways. The restrictive defect, the obstructive defect, the reduction of lung compliance and the arterial hypoxemia were relatively uncommon and probably occurred when the diseases were more advanced.