[Lung function and normal values]

Interindividual derived predicted values of lung function are not suitable for detection of early changes of lung function. Intraindividual values show variability, which should be considered. Many of the very common obstructive lung diseases start with small variations of the individual values of lung function, long time before clinical manifestation takes place. Followup of the most useful measurements (FEV1, MEF 50%, Rt und IGV%) show reliable early changes, important for preventive therapeutic intervention. Strong variability of the individual values argue for hyperreagibility of the airways, even as a risk factor for manifestation of obstructive airway diseases.