Comparison of impulse oscillometry measurements according to body mass index in patients with asthma

Obesity can lead to increased airway resistance, especially in the peripheral airways. Impulse oscillometry (IOS) may detect small airway changes in asthma. In this study, we aimed to investigate the effect of obesity on the small airways of the lungs in asthmatic patients by IOS measurements.

One hundred newly diagnosed asthmatic patients (28 male) were divided into three groups (BMI (< 25.0 kg/m²: Group-1; 25.0 to 29.9 kg/m²: Group-2; ≥30 kg/m²: Group-3). Demographic data, comorbidities, Beck anxiety and depression questionnaires, PFTs, and IOS measurements of the patients were recorded.

There was no detected significant difference concerning age, gender, smoking history, pack year, comorbidities (except hypertension and anxiety), asthma cardinal symptoms (except dyspnea), and pulmonary function tests among groups (p > 0.05). There were significant differences regarding R5, R5%, R20%, X5, X20, Fres, and R5-R20 among the three groups. Group 1 significantly differed about R5-R20, X5, AX, and Fres compared to groups 2 and 3 in pairwise comparisons. Based on these results, a difference was detected between BMI < 25 and ≥ 25. There was only one significant variable (R20%) between BMI < 30 and ≥ 30. When performing a correlation test between IOS parameters and BMI, it was observed to be significantly correlated (p < 0.05) except X5% and X20% (p > 0.05).

Obesity and being overweight affected peripheral airways and reactance; however, obesity also affects central airways, based on our results. In addition, it was thought that IOS may detect earlier than PFTs on small airway changes.