Comparison of the forced oscillation technique and the interrupter technique for assessing airway obstruction and its reversibility in children

The forced oscillation technique (FOT) and interrupter technique are partic ularly attractive for pediatric use as they require only passive cooperatio n from the patient. We compared the sensitivity and specificity of these me thods for detecting airway obstruction and its reversibility in 118 childre n (3-16 yr) with asthma or chronic nocturnal cough, FOT (R-0 and R-16) and interruption (Rint) parameters were measured at baseline and after bronchod ilator inhalation (n = 94). Rint was significantly lower than R-0, especial ly in children with high baseline values. Baseline parameters were normaliz ed for height and weight [R(SD)]. In children able to perform forced expira tory maneuvers (n = 93), the best discrimination between those with baselin e FEV1 <80% or <greater than or equal to>80% of predicted values was obtain ed with R-0(SD). At a specificity of 80%, R-0(SD) yielded 66% sensitivity, whereas Rint(SD) yielded only 33% sensitivity. Similarly, postbronchodilato r changes in R-0(SD) [DeltaR(0)(SD)] yielded the best discrimination betwee n children with and without significant reversibility in FEV1. At a specifi city of 80%, DeltaR(0)(SD) yielded 67% sensitivity and Delta Rint(SD) yield ed 58% sensitivity. In children unable to perform forced expiratory maneuve rs (n = 25), FOT, contrary to the interrupter technique, clearly identified a subgroup of young children with high resistance values at baseline, whic h returned to normal after bronchodilation. We conclude that, in asthmatic children over 3 yr old, FOT measurements provide a more reliable evaluation of bronchial obstruction and its reversibility compared with the interrupt er technique, especially in young children with high baseline values.