Exhaled nitric oxide in healthy and asthmatic children

OBJECTIVES: One of the main findings in asthma is chronic inflammation of the airway. Exhaled nitric oxide may be a useful marker of airway inflammation in asthmatic children. To evaluate the concentration of nitric oxide (NO) in exhaled air in healthy and asthmatic children and to relate this variable with different treatments. MATERIAL AND METHODS: A cross-sectional study was performed in a tertiary hospital. The concentration of exhaled NO (in parts per billion) was analyzed by chemoluminescence using the T technique of exhaling against expiratory resistance with positive mouthpiece pressure in two different study groups: group A (control group) consisted of 105 healthy children aged 6-14 years old without a history of respiratory disease; group B (asthmatic group) consisted of 79 children aged 6-14 years old diagnosed with asthma and undergoing anti-asthmatic treatment for at least the previous two months, depending on the severity of their disease. Quantitative variables were analyzed using Student's t-test and the relationship between qualitative variables was analyzed using the chi-squared test. RESULTS: Expired NO concentrations were significantly higher in the asthma group (15.02 ppb) than in the control group (5.40 ppb) (p < 0.01). No significant differences were found among the asthmatic children in asthma severity. Expired NO was higher in asthmatic children treated with nedocromil (16.62 ppb) than in those treated with inhaled corticosteroids (11.8 ppb) but this difference was not significant (p 0.08). Children who presented signs of acute asthma (22.87 ppb) and those with a positive bronchial dilatation test (20.65) showed higher expired NO values (p < 0.05) than those without asthmatic crises and/or a negative bronchial dilatation test. Likewise, children with atopic dermatitis showed higher expired NO concentrations (23.07 ppb) than those without atopic dermatitis (11.68 ppb) (p < 0.001). CONCLUSIONS: Children with asthma of various degrees of severity have higher levels of expired NO than do healthy children. Measurement of expired NO concentrations can be used to monitor bronchial inflammation and to evaluate the efficacy of anti-inflammatory treatments.