A comparison between impulse oscillometry system and spirometry for spirometry for detecting airway obstruction in children

Hur, Hae Young; Kwak, Ji Hee; Kim, Hyoung Yun; Jung, Da Wun; Shin, Yoon Ho; Han, Man Yong

Abstract

PURPOSE: Measurement of forced expiratory volume in 1 second (FEV1) is usually difficult to obtain in children under six years of age because it requires active cooperation. This study evaluates the sensitivity of impulse oscillometry system (IOS) parameters for detecting airway obstruction in comparison with FEV1.
METHODS
We studied 174 children who performed the lung function and methacholine challenge tests to diagnose asthma by IOS and spirometry. Children were divided into two subgroups according to their PC20, which is a parameter for bronchial sensitivity. We compared IOS parameters with FEV1 at the baseline, post-methacholine challenge, and evaluated their correlation.
RESULTS
At the baseline, reactance at 5 Hz (X5) and resistance at 5 Hz (R5) significantly differed between the PC20 positive (PC20< or =16 mg/mL) group and PC20 negative (PC20>16 mg/mL) group; however, FEV1, FEV1% predicted, FEV1_Zs (Z score) did not differ. FEV1 is correlated with X5 (r=0.45, P<0.01) and R5 (r=-0.69, P<0.01). FEV1_Zs is also correlated with X5_Zs (r=-0.26, P<0.01) and R5_Zs (r=-0.31, P<0.01). After the methacholine challenge test, dose-response slopes in FEV1 and X5 significantly differed between the two subgroups (P<0.05).
CONCLUSION
IOS parameters were more discriminative than FEV1 for detecting decreased baseline lung function between two subgroups and have a good correlation with FEV1.