Objective  To analyze the relationship of fractional exhaled nitric oxide (FeNO) level with asthma control and lung function in asthmatic children.

  Methods  Fifty-three children aged 4 to 12 years with asthma were selected as research objects. According to FeNO concentration measurement results, they were divided into low FeNO level group, medium FeNO level group and high FeNO level group. The control level of asthma was evaluated, and the children were divided into poorly controlled children and well controlled children according to the results. FeNO and pulmonary function related indexs optimal valuespercentage of the forced expiratory volume in one second (FEV₁) to the estimated value (FEV₁%), percentage of forced vital capacity to the estimated value (FVC%), the percentage of peak expiratory flow rate to estimated value (PEF%), the 25% percentage of peak expiratory flow rate to estimated value (PEF25%)were measured and recorded; the correlations of FeNO level with asthma control and pulmonary function were analyzed; the diagnostic value of FeNO in children with poorly controlled asthma was analyzed.

  Results  The asthma control rate of well-controlled children was significantly decreased in the low, medium and high FeNO groups (P < 0.05). FeNO was correlated with asthma control in children (P < 0.05). The area under the curve (AUC) of FeNO in children with poorly controlled asthma was 0.697, and sensitivity and specificity were 76.2% and 71.9%, respectively. There were no significant differences in pulmonary function related indexes of FeNO low level group, medium level group and high level group (P>0.05). There were no correlations of FeNO with FEV₁%, FVC%, PEF% and PEF25% (P>0.05).

  Conclusion  FeNO level is correlated with asthma control in asthmatic children. FeNO level has higher diagnostic value for children with poor control.