Alveolar exhaled nitric oxide is elevated in hereditary hemorrhagic telangiectasia

Patients with intrapulmonary shunt due to hepatopulmonary syndrome have diffuse pulmonary microvascular dilatation. Studies have shown that these patients have increased exhaled nitric oxide (NO) levels, suggesting that alveolar capillary NO production is increased. We speculated that alveolar capillary NO overproduction might have a similar mechanistic role in the development of shunting vessels, arteriovenous malformations, in hereditary hemorrhagic telangiectasia (HHT), in which 30-45% of patients have pulmonary arteriovenous malformations (PAVMs). Our objective was to determine if alveolar exhaled NO is elevated in patients with HHT compared to controls. We measured the alveolar fraction of exhaled NO (200 ml/s expiratory flow rate) in HHT subjects with and without a history of PAVMs and in healthy, nonsmoking controls with no known lung disease. We compared 58 HHT subjects to 49 healthy controls. Exhaled NO was significantly greater in HHT subjects (mean = 12.0 ppb, SD = 3.5) than in controls (mean = 10.5 ppb, SD = 3.2) (p = 0.02). We detected a significantly higher level of alveolar exhaled NO in subjects with HHT compared to healthy controls, suggesting that alveolar capillary NO production may be increased in HHT and may have a mechanistic role in PAVM formation.