Systemic sclerosis (SSc) is a chronic autoimmune disease of unknown etiology with high morbidity and mortality. SSc manifests by fibrosis of skin and internal organs. Although the underlying mechanisms are still subject to investigation, endothelial dysfunction and abnormal immune response are thought to contribute to vascular dysfunction and fibrosis in SSc.~Pulmonary involvement, such as pulmonary arterial hypertension (PAH) and interstitial lung disease (ILD) is a major cause of death in SSc. Although the 6MWT is generally used for evaluating PAH and ILD, the utility in SSc is undetermined. Several investigators have found weak or moderate correlations of 6MWT in pulmonary involvement in SSc. The 6MWT is influenced by the status of all organ systems involved in exercise (pulmonary, cardiac, peripheral vascular, neuromuscular unit and muscle metabolism) as well as by specifics of test conditions. There is a pressing need for new, practical method which corroborates the current 6MWT for the evaluation of pulmonary disease severity in SSc.~Breath-holding test (BHT) is one of the most useful methods for assessing the sensitivity of peripheral chemoreflex. Recent studies have demonstrated that BHT was correlated to pulmonary function test. BHT can be safely conducted and doctors handle a medical emergency during test easily as well. Therefore, this study evaluates the utility of BHT as surrogate marker of pulmonary involvement in patients with SSc.
This study aims to evaluate the utility of breath-holding test as a marker of pulmonary disease severity in patients with systemic sclerosis.