A role of impulse oscillometry for diagnosis of mild bronchial obstruction
The aim of this study was to investigate a role of impulse oscillometry (IO) for detection of mild bronchial obstruction. Methods. The study involved 87 patients with different respiratory diseases. Bronchial obstruction according to spirometry results was found in 50 patients (the study group). The control group patients did not demonstrate any abnormalities in spirometry, body plethysmography and lung diffusing test. Results. An abnormal increase in frequency-dependent resistive component of respiratory impedance (Rrs) at the oscillation frequency of 5Hrz and 10 Hrz [both the relative oscillation frequency (Rrs5-Rrs20)/Rrs20 and the absolute oscillation frequency (Rrs5-Rrs20)] was found in patients with mild bronchial obstruction. The resonance frequency (f<sub>res</sub>) shifted towards higher frequency; reactance area (AX) increase and expiratory airflow (DXrs5) limitation were also found in those patients. Rrs5, Rrs20, and the reactive resistance (Xrs5) were within the normal range. Conclusion. Rrs5 и Xrs5 could detect mild bronchial obstruction only in 32 % of the cases. AX is more useful parameter as it increased in 64% of the patients. The severity of bronchial obstruction diagnosed with IO or spirometry was not identical in some cases.