[Predictability of model size in impulse oscillometric airway resistance measurements in animals (calf)]

The aim of this study was to investigate the behaviour of parameters which can be obtained by a 7-component model of the lung using impulse oscillometry in calves. Seven healthy conscious calves were examined using "Master Screen IOS" (E. Jaeger GmbH & Co. KG, Würzburg/D) and the following study design: [I] baseline measurements, [II] measurements after inhalation saline, [III] measurements during carbachol-induced bronchoconstriction, [IV] measurements after bronchodilatation by fenoterol. Measurements were made individually using a rigid face mask. Examining the spectral behaviour of the respiratory impedance (5 to 35 Hz), reactance (X) was more sensitive to bronchochallenge (stages [all] and [IV]) than resistance (R). Using the 7-component model of the lung, the resistance was differentiated into a central part (Rz) and a peripheral part (Rp). Changes in Rp were more significant than changes in Rz during stages [III] and [IV]. The parameters central inertance (Lz), chest wall compliance (Cw), and lung compliance (Cl) did not change during the study. Surprisingly, the parameter called "bronchial compliance" (Cb) increased significantly during bronchoconstriction. Therefore, further research is necessary to clarify whether the model needs to be modified for general applications or only for measuring bovines.