MECHANICS OF BREATHING IN ANIMALS - PART 4 - THE DIAGNOSTICAL VALUE OF LUNG-FUNCTION TESTS USING THE IMPULSE OSCILLOMETRY SYSTEM (IOS) IN CALVES

Taking methodological and physiological aspects into account (see Part 3), the impulse oscillometry system (IOS) was found to be sensitive t o, detecting and to quantifying clinically relevant changes in respira tory mechanics in calves.' Therefore, the complex respiratory impedanc e needs to be measured in terms of resistance and reactance within the frequency range between 5 Hz and 20 Hz. The behaviour of resistance a nd reactance in dependence of frequency allows to differentiate and to localise airway obstructions. Obstructions of upper (extratharacic) a irways were mainly characterised by a frequency independent increase i n the resistance. Within the reactance curve, no change in the resonan t frequency could be observed. In a peripheral airway obstruction both resistance and reactance changed. The most typical finding concerning resistance was that a negative frequency dependence occurred. The rea ctance became more negative. Following this, the resonant frequency in creased. With progressive obstruction of the peripheral airways, the r eactance became more informative than resistance.