Bronchodilator response cut-off points and FEV (0.75) reference values for spirometry in preschoolers

OBJECTIVE: To determine the cut-off points for FEV(1), FEV(0.75), FEV(0.5), and FEF(25-75%) bronchodilator responses in healthy preschool children and to generate reference values for FEV(0.75). METHODS: This was a cross-sectional community-based study involving children 3-5 years of age. Healthy preschool children were selected by a standardized questionnaire. Spirometry was performed before and after bronchodilator use. The cut-off point of the response was defined as the 95th percentile of the change in each parameter. RESULTS: We recruited 266 children, 160 (60%) of whom were able to perform acceptable, reproducible expiratory maneuvers before and after bronchodilator use. The mean age and height were 57.78 ± 7.86 months and 106.56 ± 6.43 cm, respectively. The success rate for FEV(0.5) was 35%, 68%, and 70% in the 3-, 4-, and 5-year-olds, respectively. The 95th percentile of the change in the percentage of the predicted value in response to bronchodilator use was 11.6%, 16.0%, 8.5%, and 35.5% for FEV(1), FEV(0.75), FEV(0.5), and FEF(25-75%), respectively. CONCLUSIONS: Our results provide cut-off points for bronchodilator responsiveness for FEV(1), FEV(0.75), FEV(0.5), and FEF(25-75%) in healthy preschool children. In addition, we proposed gender-specific reference equations for FEV(0.75). Our findings could improve the physiological assessment of respiratory function in preschool children.