EVALUATION OF THE INTERRUPTER TECHNIQUE FOR THE USE OF ASSESSING AIRWAY-OBSTRUCTION IN CHILDREN

The purpose of this study was to determine if the interrupter technique, a noninvasive method for measuring airflow resistance, could be used to assess airway obstruction in children. In 107 children (74 with asthma, 12 with cystic fibrosis, and 21 without lung disease) conductance (mostly of airways) measured with the interrupter technique (G(int)) was correlated with both forced expiratory volume in 1 second (FEV,) and the forced expired flow rate between 25% and 75% of vital capacity (FEF(25-75)). In addition, 17 children with significant airway obstruction due to asthma also had airway resistance measured by body plethysmography (R(aw)) before and after treatment. Resistance and conductance measurements made with the interrupter technique were subdivided into inspiratory (R(int-insp), G(int-insp)) and expiratory (R(int-exp), G(int-exp)) values. In the 107 children, a high degree of linear correlation was found between G(int) and FEV(1); for G(int-exp), r=0.77 (P<0.001), and for G(int-insp), r=0.76 (P<0.001). There was also good linear correlation between G(int) and FEF(25-75); for G(int-exp), r=0.70 (P<0.001), and for G(int-insp), r=0.67 (P<0.001). In the 17 asthmatic children who were tested before and after treatment of their airway obstruction, R(int) correlated highly with R(aw); for R(int-exp), r=0.91 (P<0.001), and for R(int-insp,) r=0.83 (P<0.001). The pre- to post-treatment changes in R(int) and R(aw) were similar. We conclude that the interrupter techniqueinterrupter technique can be used to assess changes in airway obstruction, but normal values must be established and further investigation is required before the complete extent of its clinical utility will be known. (C) 1994 Wiley-Liss, Inc.