Increased oral nitric oxide in obstructive sleep apnoea.

BACKGROUND

Hypoxia and snoring-related mechanical trauma contribute to airway inflammation in obstructive sleep apnoea (OSA). Increased exhaled nitric oxide (FENO), an airway inflammation marker, has been reported in OSA patients. We propose the measure of NO in the oral cavity (oNO) as marker of oropharyngeal inflammation in OSA.

METHODS

We compared oNO and FENO of 39 OSA patients with those of 26 mild asthmatics (ASTHMA), 15 patients with chronic rhinitis or rhinosinusitis (CRS) and 24 healthy subjects. A special device was used for oNO measurement. Apnoea/hypopnoea index (AHI), oxygen desaturation index, mean and nadir SaO2 were calculated from the polysomnography.

RESULTS

oNO was significantly increased in OSA (104.2 95%CI 80.2-135.5ppb) as compared to ASTHMA (71.9 95%CI 56.3-91.9ppb; p=0.015), CRS (54.4 95%CI 40.2-73.7ppb; p=0.009) and healthy subjects (63.6 95%CI 59-73ppb; p<0.001). oNO was directly related to AHI (r=0.466, p=0.003) and to minutes slept with SaO2 <90% (r=0.471, p=0.011) and it was inversely related to nadirSaO2 (r=-0.393, p=0.018). FENO was highest in asthmatics (40.3 95%CI 32.5-50.1ppb) and only slightly elevated in OSA (23.1 95%CI 19,8-28.3ppb) and CRS (22.8 95%CI 16.8-32.5ppb).

CONCLUSIONS

The finding that oral NO is increased in OSA and is related to upper airway obstructive episodes and to hypoxemia severity, strengthens the clinical and pathogenic role of oral inflammation in OSA.