Reduction of <i>F</i>_ENO by tap water and carbonated water mouthwashes: magnitude and time course

Fractional exhaled nitric oxide (<i>F</i>_ENO) assesses eosinophilic inflammation of the airways, but <i>F</i>_ENO values are also influenced by oral nitric oxide (NO). The aim of this pilot study was to measure <i>F</i>_ENO and compare the effect of two different mouthwashes on <i>F</i>_ENO and analyse the duration of the effect. <i>F</i>_ENO 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 <i>F</i>_ENO immediately at the beginning compared to the baseline (<i>p</i> p ranging from &lt;0.001 to &lt;0.05). The tap water mouthwash reduced <i>F</i>_ENO 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.