ObjectiveToinvestigate the clinical significance of dynamic changes of fractional concentration of nasal exhaled nitric oxide (FnNO) in the treatment of children with chronic sinusitis (CRS).MethodsA total of 933 children with FnNO were reviewed, who were enrolled in Shenzhen Children's Hospital from 2018 to 2020. Twenty cases were included, who were the hospitalized children with CRS followed up for FnNO changes. According to the history of allergic diseases, the patients were divided into CRS with allergy group (n=10) and CRS without allergy group (n=10).The level of FnNO was measured by the Sunvou exhaled NO measuring system and the passive exhalation and silence technique.Results① The disease course of the 20 cases with chronic cough was more than 3 months, 16 cases of them with nasal congestion, and 10 cases of them with a history of allergy. ②After 36 months of follow-up, the average FnNO of 20 children with CRS was the FnNO values of 20 children before and after treatment were significantly different(150±164) PPB vs (337±280) PPB, P < 0.05. ③FnNO in CRS with allergy group was significantly higher after treatment than before treatment, and the difference was statistically significant(136±116) PPB vs (519±280) PPB, P < 0.01.There was no significant difference in FnNO before and after treatment in CRS without allergy group(164±206) PPB vs (156±120) PPB, P>0.05. ④The clinical data of 10 CRS patients without allergy showed that the level of FnNO continued to decrease in 4 cases of them, and in 3 cases of them diagnosed with primary ciliary dyskinesia (PCD), and FnNO < 77 ppb after repeated examination. And one patient of them was diagnosed with cystic fibrosis (CF).ConclusionThe FnNO level in children with CRS is often significantly, which may be related to allergy or nasal obstruction. FnNO level gradually tended to normal after regular treatment in children with CRS.The FnNO level continuously decreased in children with with CRS, who should be alert to whether they are complicated with basic diseases, such as PCD or CF.