UNLABELLEDMorbidity of chronic lung disease in young children is relatively high, and could increase in the future. Pulmonary function testing is used for clinical assessment of patients with suspected or obvious pulmonary disease to assess the severity of dysfunction and to evaluate therapeutic effectiveness. In the recent few years, forced expiratory parameters assessing lung function have been measured in older children. In order to assess abnormalities of lung function in preschool patients with respiratory disorders based on changes of forced expiratory parameters, adequate reference values are needed. However, such data in healthy preschool children remain scant in the literature.

OBJECTIVEThe aim of this study was to characterize the spirometry of preschool children and establish the normal lung function prediction equations for Chinese preschool children.

METHODSA survey in 343 healthy preschool children (184 boys and 159 girls) aged 3 to 6 years (73 children aged 3 years, 96 children aged 4 years, 91 children aged 5 years and 83 children aged 6 years) was carried out in Shenzhen in 2004. Eleven flow volume tests parameters, i.e., forced vital capacity (FVC), forced expiratory volume at 0.5 second (FEV(0.5)), forced expiratory volume at 0.75 second (FEV(0.75)), forced expiratory volume at one second (FEV(1)), maximal mid expiratory flow rate (FEF(25%-75%)), peak expiratory flow (PEF), forced expiratory time (FET100%) were measured by using COSMED spirometry produced in Italy. Stepwise multiple regressions and non-linear regressions were carried out with the statistical software SPSS10.0 for Windows to identify the best predictors of lung function parameters using standing height, weight, age and gender as potential determinants.

RESULTSSpirometric tests could be successfully carried out by using imagery methods in the following percentages of children: 69.9% of 3 to 4 years old, 70.8% of 4 to 5 years old, 92.3% of 5 to 6 years old and 91.6% of 6 to 7 years old children, 77.7% of the selected population (217/279) of children performed at least two acceptable tests respectively. The average forced expiratory time (FET) was 1.61 +/- 0.52 sec (x +/- s), the 5th percentile value was 0.9 sec, 18 of 279 (6.5%) children produced a FET less than 1 second. Forced expiratory volume in 0.50 and 0.75 sec (FEV(0.5), FEV(0.75)) were thus measured necessary in preschool children. All lung volumes and flow rates increased with age, height as well as weight growth in both gender groups. The correlation among most lung function parameters was higher in height than in age and weight in boys. Whereas the correlation among most lung function parameters was higher in age than in height and weight in girls. The regression equations of lung function were established. By comparison with the equations derived from this study and from studies by Nystad, it was found that there was a difference between the predicted values.

CONCLUSIONSpirometric testing is feasible in preschool children by using imagery methods and may be useful for both clinical practice and research. The correlation among most lung function parameters was higher in height than in age and weight in boys. Whereas the correlation among most lung function parameters was higher in age than in height and weight in girls.