Inhomogeneity of lung ventilation in children with obesity and its potential role in worsening asthma

Asthma is more frequent and severe in individuals with obesity compared to those with normal weight. While inhomogeneity of lung ventilation due to distal airway obstruction is a key feature in asthma, the effect of obesity on ventilation homogeneity is unclear. We conducted a cross-sectional study comparing lung clearance index (LCI) using multiple breath nitrogen washout technique between children with normal weight and asthma (n = 97), overweight/obesity and asthma (n = 100), overweight/obesity and no asthma (n = 100), and children with normal weight and no asthma (n = 67). Spirometry, lung volumes, and fractional exhaled nitric oxide (FeNO) were obtained for comparison. Results showed no significant difference in LCI between overweight/obesity groups and normal weight groups and no significant correlation between LCI and body mass index (BMI). However, LCI was higher in the asthma groups compared to non-asthma groups (p = 0.017, p = 0.003). There was a significant negative correlation between LCI and FEV1% predicted, FEV1/FVC, and FEF25-75% predicted (r = -0.24, p < 0.001; r = -0.26, p < 0.001; r = -0.23, p < 0.001), and a positive correlation with RV/TLC (r = 0.17, p = 0.003) and FeNO (r = 0.29, p < 0.001). These findings indicate that obesity does not affect the homogeneity of lung ventilation. Therefore, alternative mechanisms should be considered to explain the association between asthma and obesity.