[Clinical value of continuous monitoring of fraction of exhaled nitric oxide in childhood asthma].

Objective: To investigate changes in the fraction of exhaled nitric oxide (FeNO) in childhood asthma, and to evaluate the clinical value of continuous monitoring of FeNO.

Methods: Twenty children with mild to moderate asthma were enrolled from the special outpatient clinic for asthma. Follow-up was performed at 8, 16, 24, 32 and 40 weeks after treatment. At each follow-up, asthmatic symptoms were recorded, pulmonary function was evaluated and FeNO was measured.

Results: The mean FeNO decreased rapidly 8 weeks after treatment and slowly afterwards. It decreased significantly 8,16,24 and 40 weeks after treatment (P<0.01). It increased significantly during acute attacks of asthma and decreased rapidly during periods of remission. There was significant negative correlation between FeNO and forced expiratory volume in one second (r =-0.193 P<0.05). The receiver operating characteristic curve of FeNO showed that FeNO had a sensitivity of 87.9% and a specificity of 80% for uncontrolled asthma when FeNO was 35.5 ppb, and that it had a sensitivity of 97% and a specificity of 27.1% when FeNO was 20.5 ppb.

Conclusions: monitoring of FeNO can be used to evaluate the control level of airway inflammation in childhood asthma. When FeNO is less than 20.5 ppb, airway inflammation may be well controlled. When FeNO is more than 35.5 ppb, airway inflammation may be out of control. A sharp increase in FeNO suggests the possibility of acute asthma attack in children.