Eucapnic voluntary hyperventilation test decreases exhaled nitric oxide level in children

Background Exhaled nitric oxide (FeNO) measurements and eucapnic voluntary hyperventilation (EVH) tests have been used as diagnostic tools for asthma. Data on the impact of hyperventilation on the level of FeNO are limited. Aim We aimed to evaluate whether EVH tests affect the level of FeNO in children aged 10-16 years. Methods A total of 234 children aged 10-16 years had a 6-min EVH test performed. In total, FeNO values for 153 of 234 children were measured before the test and within 15 min after the test. According to a baseline FeNO level of 20 ppb, children were divided into two groups: those with low values (FeNO < 20 ppb) and those with high values (FeNO >= 20 ppb). Results The median age of the children was 13.4 years (interquartile range 12.3-15.3 years); 58% were boys and 42% were girls. Of these children, 51% were sensitized to aeroallergens. In 101 of 153 children (66%), the FeNO values decreased after the EVH test. In children with low and high baseline levels, the median level of FeNO decreased after the EVH test: 10.5 ppb before versus 9.5 ppb after (p .011), and 31.0 ppb before versus 28.0 ppb after (p .011), respectively. The decrease in FeNO after EVH test was not associated with induced bronchoconstriction expressed as a change in FEV1 (R-s = .19). Conclusions The EVH test decreases FeNO levels. Therefore, FeNO should be measured before an EVH test is performed.