Comparison of Reference Values and Short-Term Variability for Oscillatory and Spirometric Lung Function in Healthy Korean Preschool Children.

Respiratory function measurements are important in the diagnosis and follow-up assessment of respiratory diseases. The aims of this study were to establish reference values for spirometry, to compare them with respiratory resistance and impedance by an impulse oscillometry system (IOS), and to analyze 3-month follow-up studies in healthy Korean preschool children. Six hundred seven questionnaires were distributed and 497 (82%) were returned. Lung function tests were performed in 183 healthy children of the age of 3-6 years. The 3-month follow-up studies were conducted from 19 children who visited our clinic twice. Of the 183 children who underwent both IOS and spirometry, 164 (90%) and 150 (82%) met the quality-control criteria for IOS and spirometry, respectively. The regression equations of each spirometric parameter were obtained. Height was the most consistently correlated measurement in both boys and girls. All spirometry parameters, except for FEF/FVC, were significantly correlated with IOS parameters. There were no significant differences in respiratory resistance at 5 Hz measured by IOS (Rrs), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV) between the first and second sets. The intraclass correlation coefficients and relative coefficients of repeatability for FEV, Rrs, and respiratory system reactance (Xrs) were 0.90 (95% CI 0.73-0.96), 0.82 (95% CI 0.53-0.93), and 0.55 (95% CI -0.17-0.83) and 22.6%, 35.5%, and 91.8%, respectively. The obtained values and regression equations provide a reference for Korean preschool children and may be of importance in evaluating lung function of preschool children with pulmonary problems. Respiratory resistance and FEV for healthy young Korean children are lower than literature reported reference values for Caucasian children. Rrs appears to be more stable on repeat testing than Xrs.