Influence of oral care on fractional exhaled nitric oxide

BACKGROUND: Fractional exhaled nitric oxide (FeNO) is an indicator of bronchial inflammation in asthma patients. However, nitric oxide is also produced in the oral cavity, with production depending on the local anaerobic flora and intraoral acidity. OBJECTIVE: To evaluate the influence of oral care on measurement of FeNO, to investigate the influence of sleep when the oral environment changes dramatically, and to assess the impact of oral care on FeNO in the real clinical setting. METHODS: FeNO was measured before and after oral care in 14 subjects on awakening and at bedtime on 2 consecutive days to investigate variation of nitric oxide derived from the oral cavity. It was also measured before and after oral care in 62 outpatients with asthma to assess the clinical relevance of oral cavity nitric oxide. RESULTS: On both days, FeNO was significantly decreased by oral care on awakening (day 1: decrease = 10.6 ± 12.4 ppb, p = 0.0020; day 2: decrease = 11.6 ± 23.7 ppb, p = 0.0009), and the decrease was larger than at bedtime. In addition, FeNO was significantly reduced by oral care in asthma outpatients (decrease = 1.73 ± 0.95 ppb, p = 0.0090), and older age was significantly correlated with the decrease (p = 0.0261). CONCLUSION: Oral care resulted in a decrease of FeNO, especially on awakening. While nitric oxide derived from the oral cavity generally has a limited impact in outpatients with asthma, its influence on measurement of FeNO may need to be considered, especially in elderly patients.