Effect of Obesity on Airway Mechanics

Abstract

Background: Obesity is known to induce lung function impairment. Previous studies of decline in lung function associated with obesity are well established.

Materials and methods: In this cross-sectional study, to evaluate the effects of different obesity indices on lung mechanics, healthy subjects (males-23 and females-22) were recruited. Anthropometric parameters like body mass index (BMI), waist circumference (WC), hip circumference (HC) and neck circumference (NC) were measured and waist-hip ratio (WHR) was derived. Spirometry, impulse oscillometry (IOS) and fractional exhaled nitric oxide (FeNO) measurements were performed to assess lung function. Subgroups were divided and analysed.

Results: In males, increased WHR is associated with increased total airway resistance (R₅). BMI correlates positively with R₅, R₅% predicted, resistance at 20 Hz (R₂₀) and R₂₀% predicted; likewise, WHR shows a positive correlation with R₅. In females, increased WHR has significantly higher R₅, R₅% predicted, R₂₀, R₂₀% predicted, area of reactance (Ax), resonant frequency (Fres) and decreased reactance at 5 Hz (X₅), reactance at 20 Hz (X₂₀), X₂₀% predicted. The female group with higher WC shows significantly increased R₅, R₅% predicted, R₂₀, R₂₀% predicted, Ax, Fres and lower fixed ratio of forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC), X₅, X₂₀, X₂₀% predicted. The group with higher NC has a lower FEV₁/FVC ratio. WHR positively correlated with R₅% predicted and Fres while WC correlated positively with R₅, R₅% predicted, Ax and Fres; same way, NC with X₅% predicted.

Conclusion: Obesity/overweight causes significant changes in lung volumes, capacity and airway mechanics, Higher WC and WHR are associated with significant changes in lung mechanics, which are more prominent in females than in males. NC is not associated with changes in lung mechanics.

Keywords: Gender; impulse oscillometry; lung mechanics; obesity; spirometry.