Reduction of FENO by tap water and carbonated water mouthwashes: magnitude and time course.

Fractional exhaled nitric oxide (FENO) assesses eosinophilic inflammation of the airways, but FENO values are also influenced by oral nitric oxide (NO). The aim of this pilot study was to measure FENO and compare the effect of two different mouthwashes on FENO and analyse the duration of the effect. FENO was measured in 12 randomized volunteers (healthy or asthmatic subjects) with a NIOX VERO® analyser at an expiratory flow rate of 50 mL/s. After a baseline measurement, a mouthwash was performed either with tap water or carbonated water and was measured during 20 min in 2 min intervals. The procedure was repeated with the other mouthwash. We found that both mouthwashes reduced FENO immediately at the beginning compared to the baseline (p < .001). The carbonated water mouthwash effect lasted 12 min (p ranging from <0.001 to <0.05). The tap water mouthwash reduced FENO statistically significantly only for 2 min compared with the baseline. We conclude that a single carbonated water mouthwash can significantly reduce the oropharyngeal NO contribution during a 12 min time interval.