Applicability of interrupter resistance measurements using the MicroRint® in daily practice

This study was performed to evaluate the applicability of a simple device (MicroRint®) for measuring airway resistance, to derive normal values and to compare values with maximal expiratory flow volume (MEFV) parameters in asthmatic and healthy children. Repetitive R_int measurements were performed in 125 healthy children and 107 asthmatic children (age range 0.8-16.8 years). In 42 asthmatic patients R_int and MEFV values were compared and in 29 asthmatic children bronchodilation testing was performed. Successful R_int measurements were possible in 91% of the children.The mean coefficient of variation of repeated measurements was 7.1 (±6.1)%. R_int values of healthy children showed a significant curvilinear correlation with age (r=-0.80, P < 0.001) and height (r=-0.81, P <0.001). In asthmatic and healthy children R_int values were comparable. A significant inverse correlation was found between R_int and MEFV values (for FEV₁ and R_int r=-0.80, P < 0.001). After bronchodilation there was a significant increase in FEV₁ and decrease in R_int, but changes between the two parameters did not correlate. In conclusion, the interrupter technique is feasible and repeatable in children and has a significant correlation with other parameters of airway caliber. Baseline values do not discriminate healthy from asthmatic children.