Measurements of interrupter resistance: reference values for children 3-13 yrs of age

The interrupter technique is a convenient and sensitive technique for studying airway function in subjects who cannot actively participate in (forced) ventilatory function tests. Reference values for preschool children exist but are lacking for children >7 yrs. Reference values were obtained for expiratory interrupter resistance (R(int,e)) in 208 healthy Dutch Caucasian children 3-13 yrs of age. A curvilinear relationship between R(int,e) and height was observed, similar to published airways resistance data measured by plethysmography. No significant differences in cross-sectional trend or level of R(int,e) were observed according to sex. It was found that Z-scores could be used to express individual R(int,e) values and to describe intra- and interindividual differences based on the reference equation: 10logR(int,e)=0.645-0.00668x standing height (cm) kPa x L(-1) x s(-1) and residual SD (0.093 kPa x L(-1) x s(-1)). Expiratory interrupter resistance provides a tool for clinical and epidemiological assessment of airway function in a large age range.