Spirometry in preschool children: time has come for new reference values.

Lung function measurements play an essential role in early diagnosis and monitoring of bronchial asthma in children. For clinical evaluation, measurements are commonly compared to reference values. However, these reference values are calculated based on measurements performed in groups of mostly older children and young adults two or three decades ago. In the present, cross-sectional study, lung function measurements were performed in 518 children (241 boys and 277 girls; mean age 6.0+/-0.3 years) at a regular medical check prior to school enrollment. Spirometry was done using the MasterScreen IOS (Cardinal Health, Wurzburg). We recorded forced vital capacity (FVC), forced expiratory volume in one second (FEV(1)), maximal expiratory flow (PEF), and maximal expiratory flow at 75, 50, and 25% of vital capacity (MEF(75), MEF(50), MEF(25)). We found that FEV(1) and FVC corresponded to reference values (101.0+/-14.9% and 95.4+/-13.6%, in boys and girls, respectively). In maneuvers satisfying ATS/ERS criteria (T(E) >1 sec), forced expiratory (parameters (PEF, MEF(50)) reached only 68.9+/-13.6 and 75.9+/-26.6% of reference values, in boys and girls, respectively). There was no significant correlation of lung function parameters to BMI. In conclusion, the hitherto reference values largely overestimate the maximal flow rates of preschool children performing a forced spirometry with T(E) >1 sec. At the age of 6, forced expiratory flow values are not (yet) impaired by an increased BMI. Standardized spirometry starting in preschool children allows closely evaluating the individual development of lung function during follow-up measurements.