Impulse Oscillometry Reveals Predominantly Mechanical Drivers of Small Airway Dysfunction in Obese Children

Background: Childhood obesity can cause changes in respiratory mechanics, particularly in the peripheral airways. This study aimed to evaluate impulse oscillometry (IOS) parameters in obese children and to investigate the relationship between small airway function and metabolic indicators. Methods: A total of 135 children and adolescents (56.3% female) were included in the study. Seventy participants were obese, and 65 were in the normal-weight control group. IOS parameters (R5, R20, R5-R20, X5, X20, AX, Fres) were compared between the two groups. Obese participants were further divided into subgroups based on HOMA-IR levels, with and without metabolic disorders. The relationships between IOS parameters and body mass index z-score, HOMA-IR, and HbA1c were evaluated using correlation analysis. Results: The R5 value was significantly higher in the obese group compared to the control group (p = 0.01). The R20 parameter and R5-R20 parameter were markedly increased in the obese group (p = 0.03 and p < 0.001, respectively). The AX value was also significantly higher in the obese group (p = 0.02). No significant differences were found between the groups in terms of X5, X20, and Fres (p > 0.05). In the metabolic sub-analysis of the obese group, IOS parameters did not differ according to metabolic status. However, a weak positive correlation was found between HOMA-IR and R5-R20 (r = 0.257, p = 0.031) and AX (r = 0.290, p = 0.015). A moderate positive relationship was found between BMI z-score and R5-R20 (r = 0.424, p < 0.001) and AX (r = 0.383, p = 0.01). Conclusions: Small airway dysfunction was detected in obese children. The findings suggest that mechanical factors may be more dominant than metabolic factors in peripheral airway involvement.