Abnormal exhaled ethane concentrations in scleroderma

Scleroderma (systemic sclerosis) is a chronic multisystem autoimmune disease in which oxidative stress is suspected to play a role in the pathophysiology. Therefore, it was postulated that patients with scleroderma would have abnormally high breath ethane concentrations, which is a volatile product of free-radical-mediated lipid peroxidation, compared with a group of controls. There was a significant difference (p <0.05) between the mean exhaled ethane concentration of 5.27 pmol ml^-1 CO₂ (SEM =0.76) in the scleroderma patients (n =36) versus the mean exhaled concentration of 2.72 pmol ml^-1 CO₂ (SEM =0.71) in a group of healthy controls (n = 21). Within the scleroderma group, those subjects taking a calcium channel blocker had lower ethane concentrations compared with patients who were not taking these drugs (p =0.05). There was a significant inverse association between lung diffusion capacity for carbon monoxide (per cent of predicted) and ethane concentration (b = -2.8, p =0.026, CI = -5.2 to -0.35). These data support the presence of increased oxidative stress among patients with scleroderma that is detected by measuring breath ethane concentrations.