Abstract: 　Objective　To explore the significance and application value of fractional exhaled nitric oxide (FeNO) in children with bronchiolitis. Methods　A total of 49 hospitalized children with primary bronchiolitis admitted from January to September 2018 were selected as study subjects. According to the respiratory syncytial virus (RSV) test results, they were divided into RSV group (27 cases) and non-RSV group (22 cases). In addition, 17 healthy children of the same age were selected as the healthy controls. Nitric oxide in exhaled breath was detected by tidal breathing method in each group. Children in RSV group and non-RSV group were tested again in the remission period (1-2 weeks) and the recovery period (4-6 weeks), and the results were compared. Results　There was no difference in sex and age among RSV group, non-RSV group and control group (P>0.05). The FeNO levels in both RSV group and non-RSV group were statistically significantly different among the acute, remission and recovery phases (P<0.05). During the recovery period, there was significant difference in the FeNO levels among RSV group, non-RSV group and healthy control group (P<0.05), with RSV group having the highest FeNO levels. There was no difference in the FeNO levels among the three groups in either acute phase or remission phase (P>0.05). Conclusions　The FeNO levels in children with bronchiolitis having or not having RSV infection in both acute and remission phases were not different from those of healthy children at the same age, and were higher during the recovery phase than those of healthy children at the same age.

Key words: fractional exhaled nitric oxide;　bronchiolitis;　child