Children with smoking parents have a higher airway resistance measured by the interruption technique.

Children exposed to environmental tobacco smoke, during or after pregnancy, are known to have decreased lung function. So far this has been measured using spirometry in schoolchildren and invasive techniques in newborns. The interruption technique (Rint) is a noninvasive technique to measure airway resistance in preschool children. Our aim in this study was to investigate the effect of passive smoke exposure on Rint values in preschool and school-aged children. Rint values were obtained from 557 children in two nursery and two primary schools in the north of the Netherlands. Besides information on parental smoking habits, we collected data on characteristics that might affect airway resistance (respiratory symptoms, atopy, and family history for asthma), using a short questionnaire. Multiple linear regression was used to estimate the associations of these characteristics with Rint, for the whole group as well as for the preschool group separately. Atopy or a positive family history for asthma did not affect Rint values in the total group of 4-12-year-olds. However, as may be expected, height, age, weight, and having respiratory symptoms were associated with Rint. Moreover, Rint was significantly increased if parents smoked three or more cigarettes a day in the presence of their child. This result remained after subgroup analysis in the preschool children (4-6 years old). We conclude that passive smoke exposure is associated with a significantly higher airway resistance in preschool and school-aged children measured by Rint.