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Background: Impulse oscillometry (IOS), a new respiratory impedance measurement, is increasing in its popularity as a means to assess airway resistance in young children. Its great advantage lies in its effortless and fast performance, making the airway obstruction measurement easier for patients who are not able to perform spirometry tests. However, studies comparing spirometry with IOS in Thai children are rare.

Aims: To evaluate the correlation between IOS and spirometry parameters in Thai childhood asthma

Methods: Vyntus IOS (JEAGER^®, Germany) and spirometry tests (Vyntus SPIRO) were performed in 48 children, aged 5-15 years old, who fulfilled the GINA asthma criteria. The study, approved by the hospital’s ethics committee, was conducted between March 1, 2020 and March 31, 2021 at the Queen Sirikit National Institute of Child Health, Thailand. (TCTR20220527005)

Results: Forty-eight childhood asthma patients with a median age of 10.79 (IQR = 8.41, 11.87) years underwent both IOS and spirometry measurements. Male sex was predominant (64.58%), and 77% of patients had well-controlled asthma (C-ACT score ≥20). In our study population, the atopic comorbidities were allergic rhinitis (91.67%), atopic dermatitis (10.42%) and food allergy (10.42%). Moreover, parental asthma was found in 16.67% of the participants. In comparison with spirometry, the percentage change of FEF_25-75% was significantly negatively correlated with R5, R10, AX, and mean R5-R20 (r = -0.608, -0.528, -0.500, -0.511, respectively; p <0.001). Likewise, FEV1 was significantly negatively correlated with R15 and R20 (r = -0.520, -0.565, respectively; p <0.001). The linear regression prediction model demonstrated that a 30% increase in FEF_25-75% was related to a 22.7% reduction in R5 (p = 0.007).

Conclusion:  The percentage change of FEF_25-75% was found to negatively correlate in statistically significant terms with R5 in Thai childhood asthma. Hence, IOS is an effective and feasible replacement for spirometry as a measurement modality of lung function, especially in young children.