Vilmann L, et al. - This study was implemented to assess the feasibility of measuring fractional exhaled nitrogen oxide (FeNO) and multiple breath nitrogen washout (N₂MBW) in preschool healthy and asthmatic children. Furthermore, their capacities for discriminating between children with asthma and healthy controls were also compared. Findings demonstrated that feasibility of measuring FeNO was highly age-dependent and not applicable in children under age 4. Data also showed the feasibility of N₂MBW in the majority of preschool children. children with asthma and healthy controls could be differentiated by conductive ventilation heterogeneity (S_cond), but not FeNO.