Increased alveolar nitric oxide concentration is related to nocturnal oxygen desaturation in obstructive sleep apnoea

Abstract Purpose To assess distal/alveolar inflammation in patients with suggestive symptoms of obstructive sleep apnoea (OSA) using exhaled nitric oxide (NO) measured by two-compartment model (2-CM) after correction for axial NO back-diffusion (trumpet model). Methods Ninety five patients suspected for OSA prospectively underwent pulmonary function test, overnight polysomnography (PSG), and exhaled NO measurement. Patients with apnoea–hypopnoea index (AHI)  Results Alveolar NO concentration (C ANO ) was significantly higher in OSA patients (n = 71; 4.07 ± 1.7ppb) as compared with non-OSA subjects (n = 24; 2.24 ± 1.06ppb; p  awNO ) and fractional exhaled NO (F ENO ) did not differ between the two groups. C ANO was strongly associated to AHI (r = 0.701; p  2  1%) was 0.865 ± 0.036 (95% IC, 0.793–0.937; p  ANO at 4.5 ppb could detect these patients with specificity of 94% and sensitivity of 46%. Increase of C ANO measured after PSG was significantly related to oxygen desaturation index (ST-90%) in OSA patients. Conclusions Increased alveolar NO concentration was related to the severity of nocturnal oxygen desaturation in patients with OSA, linking the distal airway inflammation to intermittent hypoxia. (250 words)