Exhaled nitric oxide (FeNO) in cystic fibrosis (CF) patients is reduced when compared with healthy people, and it has now been found that FeNO has a relative association with airway clearance index. Studies have shown the role of some infections in changing the FeNO level; however, the role of respiratory infections in FeNO has not yet been thoroughly studied.
The objective of this study was to investigate the possibility of FeNO usage to monitor the infections in CF patients.
This cross-sectional case-control study was conducted on CF patients between the age of five to 18 with positive sputum culture, through simple non-random census method. FeNO levels were measured in 30 healthy children and 30 CF children with positive sputum culture. CF patients were treated by antibiotic therapy for two weeks; in the case offending negative sputum culture, the FeNO level was re-measured. FeNO levels were re-evaluated in 13 patients after four weeks.
There was no statistical difference between both groups in terms of age and weight. The level of FeNO in CF patients was significantly lower than in healthy children (22.1 ± 10.1 versus 30.0 ± 11.0 in the control group and P = 0.003). In 27 children, two weeks after administration of antibiotic therapy, sputum culture was negative. The mean of FeNO in these patients was 16.4 ± 5.5 at the time of the negative sputum culture, which was significantly lower than FeNO before starting the treatment. (P: 0.003). The mean FeNO was 13.0 ± 7.41 in 13 patients who were re-measured four weeks after starting the treatment. There was no significant difference between FeNO level two weeks after treatment and four weeks after starting treatment (P: 0.292). Patients with pseudomona sputum culture were not significantly different from those with non-pseudomona sputum culture in terms of primary FeNO and FeNO changes after the treatment (P value: 0.084 and 0.094, respectively).
However, in our study, FeNO was decreased after administration of antibiotic treatment in CF patients, but according to the sample size and conflicting or similar results in other studies, currently, FeNO levels cannot be used as a way of monitoring the treatment of infection in CF patients.