Increased oral nitric oxide in obstructive sleep apnoea

Hypoxia and snoring-related mechanic trauma contribute to airway inflammation in obstructive sleep apnoea syndrome (OSAS). Several studies reported increased inflammatory markers in OSAS lower airways, including exhaled nitric oxide (FENO). We propose the measure of NO in the oral cavity (oNO) as marker of oropharyngeal inflammation in OSAS. Methods- We evaluated oNO and FENo in 39 OSAS patients, 26 asthmatics (ASTHMA), 15 upper airway diseases patients (UAD) and 24 healthy subjects. oNO was measured with a device isolating the oral cavity from the nose and the lower airway. Apnoea/hypopnoea index (AHI), oxygen desaturation index, mean and nadir SaO2 were calculated from the polysomnography. Results - oNO was significantly increased in OSAS (104.2 95%CI 80.2-135.5 ppb) as compared to ASTHMA (71.9 95%CI 56.3-91.9 ppb),and UAD (54.4 95%CI 40.2-73.7 ppb). oNO was directly related to AHI (r=0.466, p=0.003) and inversely related to nadirSaO2 (r=-0.393, p=0.018). FENO was highest in asthmatics (40.3 95%CI 32.5-50.1 ppb) and only slightly elevated in OSAS (23.1 95%CI 19,8-28.3 ppb) and UAD (22.8 95%CI 16.8-32.5 ppb). Conclusions Increased oNO supports the role of oral inflammation in OSAS. The correlation between oNO, nadirSO2 and AHI reinforce the link between local inflammation, hypoxia and severity of the disease.