Fig. 3

Timecourse of FeNO at baseline and at the short and long-term follow-up: the mean FeNO decreased after FESS (43.1–26.6 ppb) in 84 % of patients who performed the analysis both before and after FESS. However after 27 ± 7 months higher levels of FeNO were again detected (FeNO = 37.7 ppb at 27 months).