Abstract: Objective To explore the correlation between impulse oscillometry (IOS) and routine pulmonary function tests (PFT) in asthmatic children. Methods The children with asthma visited from May to December 2019 were included as the research objects. On the same day of visiting, IOS and subsequent PFT test were performed to analyze the correlation between the two different lung function test methods. Results A total of 180 children ( 109 boys and 71 girls) were included and a median age was 8 years. During the acute stage, the airway resistance at 5 Hz (R5), resistance at 5 Hz minus resistance at 20 Hz (R5-R20), the absolute value of reactance at 5Hz (|X5|) and the resonant frequency (Fres) were significantly higher than those in the chronic stage and clinical remission stage, and the differences were statistically significant (P< 0 . 01 ). In the group of 3 - 6 year age, the forced expiratory volume in 1 second (FEV 1 ) is strongly correlated with R 5 , R5 -R20 and |X 5 |. Furthermore, the one-second rate (FEV 1 /FVC) is strongly correlated with R 5 and R 5 -R 20 . At the group of 7 - 15 year age, FEV 1 and R 5 were moderately correlated, and FEV 1 /FVC was moderately correlated with R 5 and R 20 . Conclusions There was a good correlation between IOS and PFT in asthmatic children, especially in the group of 3 - 6 year age. IOS is better reflect peripheral small airway function and is more sensitive than PFT.

Key words: impulse oscillometry lung function; pulmonary function tests; asthma; child