Assessment of ventilation distribution in overweight and obese children with asthma using electric impedance tomography: a cross-sectional study

Background Several studies have demonstrated an association between excessive body weight and asthma in children, underlining the link between obesity and resistance to treatments. The aim of this study is to investigate the pattern of ventilation distribution and to assess the response to bronchodilator (BD) in a cohort of overweight/obese children with asthma, using standard spirometry and Electric Impedance Tomography (EIT). Methods Single-centre, cross-sectional study. Eligible children with asthma and excessive weight were enrolled during outpatient follow-up; EIT and spirometry were performed before and after the administration of 400 & micro;g of inhaled salbutamol. Results A FEV1 < -1.64 z-score was found in 2/27 (7.4%) children (median age 12.4 yrs, 7 females); four children (14.8%) fulfilled the criteria for airway dysanapsis. Through EIT, a greater ventilation distribution was identified in the dorsal regions of the lungs. After BD, an increase in FEV1 z-score was observed, however, only 8/27 (29.6%) children reported a significant bronchodilation at spirometry; the median total %GI index and total %RVD40 remained unchanged, while a significant reduction in the VL %ROI was observed. No significant correlations were observed between pre-post BD differences in FEV1 z-score, %GI index, %RVD40 and anthropometric measures. Conclusion Children with asthma and excessive weight had a peculiar pattern of regional ventilation distribution. BD administration generally resulted in a suboptimal spirometric response, with no significant changes in EIT measurements. The relatively limited response to BD could have several interpretations, and future studies are needed to better understand the mechanisms behind these findings.