Tidal off-line exhaled nitric oxide measurements in a pre-school population

Abstract

Exhaled nitric oxide (ENO) is used as a non-invasive marker of airway inflammation. The aim of this study was to measure ENO in a pre-school population using a relatively novel method, the off-line tidal breathing method, and to investigate differences in ENO between subjects with different presentations of wheezing. ENO was measured in 129 children (median age 4.4 years, quartiles 4.0–4.8 years) through a mouth mask attached to a two-way valve with an expiratory resistance of 5 cm H₂0. Mean tidal ENO concentration (tENO) was calculated from triplicate measurements. Mean ± SEM tENO for 89 control subjects was 13±0.4 ppb (95%CI 11.8–13.7 ppb); this level was significantly different from tENO in 15 children with a history of recurrent wheezing (18.6±1.9 ppb; 95%CI 14.5–22.7 ppb; t -test P t -test P =0.0024). Conclusion:the off-line tidal breathing method is a feasible and appealing method for measuring exhaled nitric oxide in pre-school children. With this method, higher tidal exhaled nitric oxide levels were found in children with recurrent wheezing.