For the oscillometry (IOS) of the respiratory tract the Master Screen IOS VIASYS was used, the examinee breathed quietly through the mouthpiece with his/her nose closed for a period of 1 minute. In this way we measured the impedance Z at 5 Hz, the resistance to 5,10,20 Hz respectively, the reactance in 5,10,20 Hz respectively, the central and peripheral airway resistance and resonant frequency.