Influence of Mouthwashes on Extended Exhaled Nitric Oxide (FENO) Analysis

Fractional exhaled nitric oxide (F-ENO) is used to assess eosinophilic inflammation of the airways. F-ENO values are influenced by the expiratory flow rate and orally produced NO. We measured F-ENO at four different expiratory flow levels after two different mouthwashes: tap water and carbonated water. Further, we compared the alveolar NO concentration (C-ANO), maximum airway NO flux (J(awNO)) and airway NO diffusion (D-awNO) after these two mouthwashes. F-ENO was measured in 30 volunteers (healthy or asthmatic) with a chemiluminescence NO-analyser at flow rates of 30, 50, 100 and 300mL/s. A mouthwash was performed before the measurement at every flow rate. The carbonated water mouthwash significantly reduced F-ENO compared to the tap water mouthwash at all expiratory flows: 50mL/s (p<.001), 30mL/s (p=.001), 100mL/s (p<.001) and 300mL/s (p=.004). J(awNO) was also significantly reduced (p=.017), however, there were no significant differences in C-ANO and D-awNO. In conclusion, a carbonated water mouthwash can significantly reduce oropharyngeal NO compared to a tap water mouthwash at expiratory flows of 30-300mL/s without affecting the C-ANO and D-awNO. Therefore, mouthwashes need to be taken into account when comparing F-ENO results.