Reference values of Forced Expiratory Volumes and pulmonary flows in 3-6 year children: a cross-sectional study.

Background: The aims of this study were to verify the feasibility of respiratory function tests and to assess their validity in the diagnosis of respiratory disorders in young children. Methods: We performed spirometry and collected information on health and parents' lifestyle on a sample of 960 children aged 3 - 6. Results: The cooperation rate was 95.3%. Among the valid tests, 3 or more acceptable curves were present in 93% of cases. The variability was 5% within subjects in 90.8% of cases in all the parameters. We propose regression equations for FVC ( Forced Vital Capacity), FEV1, FEV0.5, FEV0.75 ( Forced Expiratory Volume in one second, in half a second and in 3/4 of a second), and for Maximum Expiratory Flows at different lung volume levels (MEF75, 50, 25). All parameters are consistent with the main reference values reported in literature. The discriminating ability of respiratory parameters versus symptoms always shows a high specificity (> 95%) and a low sensitivity (< 20%) with the highest OR ( 10.55; IC95% 4.42 - 25.19) for MEF75. The ability of FEV0.75 to predict FEV1 was higher than that of FEV0.50: FEV0.75 predicts FEV1 with a determination coefficient of 0.95. Conclusion: Our study confirms the feasibility of spirometry in young children; however some of the current standards are not well suited to this age group. Moreover, in this restricted age group the various reference values have similar behaviour.