The interrupter technique to assess airway responsiveness in children with cystic fibrosis

The aim of this study was to assess the validity of the interrupter technique (R int ) in measuring airway responsiveness in children with cystic fibrosis. Fifty children (aged 6–16 years) with cystic fibrosis performed six R int measurements followed by three acceptable forced expiratory maneuvers. Each child then inhaled 5 mg of nebulized salbutamol by facemask. After 20 min the R int and forced expiratory measurements were repeated. In the population as a whole a moderate but significant correlation between inverse R int and FEV 1 values was observed, both before and after inhaled bronchodilator (r = 0.71 and 0.72, respectively, P  < 0.001). However, when changes in R int and FEV 1 readings following inhaled bronchodilator were examined, no relationship was seen. Indeed, the two methods identified completely different subsets of children as being bronchodilator responsive. These results indicate that although a relationship exists between R int and FEV 1 in the whole population, this is not the case in individual children. R int and FEV 1 reflect different aspects of lung function. It is not appropriate to use R int as a simple alternative for FEV 1 in children with cystic fibrosis when assessing airway responsiveness. Pediatr Pulmonol. 2007; 42:23–28. © 2006 Wiley‐Liss, Inc.