Endogenous pulmonary nitric oxide production measured from exhaled air is increased in patients with severe cirrhosis

Endogenous pulmonary nitric oxide production may be increased in severe cirrhosis and contribute to pulmonary vasodilation. This study assessed pulmonary nitric oxide production by measuring nitric oxide in the exhaled air in patients with severe cirrhosis and examined the relationship between exhaled nitric oxide and pulmonary hemodynamics in these patients. Methods: Nitric oxide concentrations and production were measured in the exhaled air in six Child-Pugh class C patients with cirrhosis and 21 non-smoking healthy controls. Systemic and pulmonary hemodynamics were measured in patients only. Results: Nitric oxide concentration (32.0±1.7 (mean±SEM) vs. 8.9±1.0 ppb) and production (9.2±1.3 vs. 3.1±0.3 nmol/min) in exhaled air were significantly higher in patients than in controls. Patients had high cardiac output (8.5±0.9 l/min), low pulmonary and systemic vascular resistance (57±10 and 767±93 dyn • s • cm-5, respectively) under baseline conditions. A significant negative correlation was found between pulmonary vascular resistance and exhaled nitric oxide production (r=0.943, p=0.05) but not between cardiac output or systemic vascular resistance and nitric oxide measured in exhaled air. Conclusions: Endogenous pulmonary nitric oxide production measured from exhaled air is increased in patients with cirrhosis and liver failure. Increased nitric oxide production may also contribute to cirrhosis-induced pulmonary vasodilatation.