Exhaled nitric oxide in systemic sclerosis: Relationships with lung involvement and pulmonary hypertension

Objective. To measure nitric oxide (NO concentration in exhaled air of pati ents with systemic sclerosis (SSc) and to investigate its relationships wit h lung involvement, complicated or not by pulmonary hypertension (PH). Methods. Exhaled NO was measured by chemiluminescence in 47 patients with S Sc (16 with PH) and in 30 controls. All the patients underwent Doppler echo cardiography to assess pulmonary artery pressure (PAP), lung function tests , and thin section computed tomographic scans of the lung to quantify the e xtent of fibrosing alveolitis. Results. Exhaled NO levels were higher in patients with SSc (16.6 +/- 9.1 p pb), particularly those with interstitial lung disease (ILD) (18.3 +/- 10.4 ppb), compared to controls (9.9 +/- 2.9 ppb; p < 0.0001). In patients with PH, exhaled NO was less than in patients without PH (10.7 +/- 5.9 vs 19.6 +/- 9 ppb, respectively; p < 0.001), and patients with PH without no had ev en lower exhaled NO than patients with PH and ILD (6.6 +/- 1.1 vs 12.6 +/- 6.3 ppb; p = 0.004). There was an inverse correlation between PAP and exhal ed NO (r = -0.53, p = 0.004). Exhaled NO was not correlated to age, disease duration, current therapy, or form of disease (limited or diffuse). Conclusion, The increased concentration of exhaled NO in patients with SSc may reflect respiratory tract inflammation. The relatively low value of exh aled NO in patients with PH and the negative correlation between PAP and ex haled NO suggest the important role of NO in regulating pulmonary vascular resistance in patients with SSc.