Exhaled nitric oxide in interstitial lung diseases

• We measure exhaled NO levels in patients with idiopathic interstitial pneumonias.
• Patients have higher levels of exhaled NO than healthy controls.
• Alveolar concentration of NO is inversely correlated with lung function parameters.
• Alveolar concentration of NO could be a potential biomarker of disease severity.

Nitric oxide (NO) is a biomarker of nitrosative stress, which is involved in the pathogenesis of idiopathic interstitial pneumonias (IIP). This study evaluates exhaled NO levels in IIP patients and relates alveolar concentrations of NO (CalvNO) to pulmonary function test (PFT) and 6-minute walking test (6MWT) parameters. We measured fractional exhaled nitric oxide (FeNO), CalvNO and maximum conducting airway wall flux (J’awNO) in 30 healthy subjects and 30 patients with IIP (22 idiopathic pulmonary fibrosis and 8 idiopathic non-specific interstitial pneumonias). IIP patients had higher FeNO at flow rates of 50–100–150 ml/s and higher CalvNO levels than healthy controls (p < 0.0001). CalvNO was significantly correlated with 6-minute walking distance (p < 0.0001), recovery time (p < 0.0005), TLC (p < 0.001), FVC (p = 0.01) and TLCO (p < 0.01). IIP patients showed abnormal nitric oxide production, probably due to lung fibrosis and oxidative-mediated lung injury. CalvNO was correlated with PFT and 6MWT parameters and is proposed as a potential biomarker of lung fibrosis and exercise tolerance.