Monitoring of oral and nasal exhaled nitric oxide in eosinophilic chronic rhinosinusitis: a prospective study.

Background: We aimed to examine the effect of different therapeutic modalities on levels of fractional concentrations of exhaled nitric oxide (FeNO) in patients with eosinophilic chronic rhinosinusitis (ECRS).

Methods: Thirty-six ECRS patients with nasal polyps were treated either medically or surgically. Oral and nasal FeNO levels were measured using an electrochemical NO analyzer initially and at 1 and 6 months. The mRNA expression and localization of nitric oxide synthase (NOS) isoforms in sinus mucosa and nasal polyps were analyzed by real-time polymerase chain reaction (PCR) and immunohistochemistry.

Results: The mean oral FeNO levels in the surgical group had decreased significantly from 50.9 to 36.8 ppb 6 months after endoscopic sinus surgery. All patients in this group showed significantly higher nasal FeNO levels after treatment. The mean nasal FeNO levels were 62.3 ppb at 1 month and 93.6 ppb at 6 months. Mean oral and nasal FeNO levels in the medical group after treatment remained unchanged when compared with the baseline levels. Positive immunoreactivity of inducible NOS (iNOS) was observed in both epithelial cells and submucosal inflammatory cells. Real-time PCR analysis showed significant up-regulation of iNOS and IL-5 mRNA expression.

Conclusion: A combination of oral and nasal FeNO measurements is useful to monitor the extent of inflammation in CRS patients. The increase in nasal FeNO in the surgical group indicates prompt recovery of NO release from healed sinus mucosa through the opened sinus ostia. Reduction of oral FeNO levels may reflect a cessation of the underlying lower airway inflammation that is characteristic of ECRS.