Assessment and validation of bronchodilation using the interrupter technique in preschool children

Objective: To determine and validate a cut-off value for bronchodilation using the interrupter resistance (Rint) in preschool children. Patients and Methods: Rint was measured in 60 healthy children (age range 2.7-6.4 years) before and after salbutamol inhalation (200 mu g). Four potential methods for assessing BDR were evaluated: percent change from baseline, percent change of predicted values, absolute change in Rint, and change in Z-score. These cut-off values, determined as the fifth percentile of the healthy group, were applied to children referred for the assessment of recurrent wheezing, classified on the basis of acute symptoms and/or abnormal chest examination into symptomatic (n = 60, age range 2.9-6.1 years) and asymptomatic (n = 60, age range 2.5-5.7 years) groups. Results: The cut-off values for bronchodilation calculated in healthy children were: -32% baseline; -33% predicted; -0.26 kPa L(-1) sec; and -1.25 Z-scores. Assessing BDR in children with a history of wheezing by either a decrease in absolute Rint or a decrease in Z-score gave sensitivity, specificity, negative predictive value, and positive predictive value all >80% for detecting children with current respiratory symptoms. Conclusions: Both a decrease in Rint >= 0.26 kPa L(-1) sec and a decrease in Z-score of >= 1.25 are appropriate for assessing BDR in preschool children with a history of recurrent wheezing. As Z-score is a more general solution, we recommend using a change in Z-score to determine BDR in preschool children. Further longitudinal studies will be required to determine the clinical utility of measuring BDR in managing lung disease in such children. Pediatr Pulmonol. 2010; 45:633-638. (C) 2010 Wiley-Liss, Inc