Interrupter resistance in preschool children - Measurement characteristicsand reference values

There is a need for quick, reliable, and noninvasive lung function tests to assess airway obstruction in preschool children both for pediatric pulmona ry care as well as for research purposes. We studied feasibility, reproduci bility, and validity of measurements of the respiratory system using the in terrupter technique (interrupter resistance [Rint]) and obtained reference values in children from a general population, 2 to 7 yr of age. Accuracy wa s studied by comparisons of Rint with plethysmographic airway resistance (R aw) in 20 patients (7 to 14 yr) with mild to severe chronic airways obstruc tion and was satisfactory in patients with FEV1 > 60% predicted. The techni que proved sensitive enough to detect changes in airway caliber within a sm all group of 12 children who developed mild respiratory tract infections. A mong children from a general population, subgroups with mild respiratory sy mptoms or mild respiratory disease had higher mean Rint values. Airway obst ruction was better detected using expiratory rather than inspiratory interr uptions, both programmed at peak tidal ventilatory flow. Reproducibility wi thin subjects was satisfactory (intraclass correlation 0.82 and 0.79). The same applied to interobserver agreement (intraclass correlation 0.98). The interrupter technique proves to be a reliable and practical test of airway function, suitable for clinical and epidemiologic studies in preschool chil dren.