Introduction: Bronchiectasis is a chronic respiratory disease that causes airway inflammation and destruction, and airflow limitation reflects the disease severity in bronchiectasis. Impulse oscillometry (IOS) is a noninvasive method to estimate lung function and airway resistance using sound waves.

Objectives: The aim of this study was to identify the usefulness of IOS for predicting the disease severity in bronchiectasis.

Methods: We retrospectively reviewed the IOS parameters, clinical characteristics, and results of other examinations in 145 patients with bronchiectasis between March 2020 and May 2021. The severity of disease was assessed through FACED score. The patients were divided into two groups, a mild group and a moderate/severe group based on the FACED score three points.

Results: Fourty-four patients (30.3%) were in the moderate/severe group and 101 patients (69.7%) were in the mild group. Patients with moderate/severe severity of bronchiectasis had higher airway resistance at 5 Hz (R5) (p = 0.001), difference between the resistance at 5 and 20 Hz (26.2 vs 43.5, R5 - R20) (p < 0.001), resonant frequency (fres) (p < 0.001), and reactance area (AX) (0.68 vs 2.46, p < 0.001) than patients with mild severity. In the multivariate regression analysis, R5, R5-R20, and AX were identified as significant predicting factors for bronchiectasis severity. The area under the receiver operator characteristic curve (AUC) was 0.859 for the severity of bronchiectasis.

Conclusions: IOS parameter could reflect airway resistance in patients with bronchiectasis, especially in peripheral airway resistance. Furthermore, IOS results are useful for predicting the disease severity of bronchiectasis.