Regional lung function testing in children using electrical impedance tomography

To evaluate regional lung function in lung-healthy children before and after exercise challenge using electrical impedance tomography (EIT).

Regional lung function was examined using EIT in 100 lung-healthy children (three age subgroups: 74-121, 122-155, 156-195 months) at baseline and 10 min after exercise. Global lung function was assessed by spirometry using Z-Scores of FEV₁ , FVC, FEV₁ /FVC, and FEF₇₅ . The same lung function measures were determined in 912 EIT image pixels to enable the spatial and temporal ventilation distribution analysis. Coefficients of variation (CV) of these pixel values were calculated and histograms of pixel FEV₁ /FVC and times required to exhale 50% and 75% of pixel FVC (t₅₀ and t₇₅ ) generated. Additionally, we compared the findings of the studied population with three cystic fibrosis (CF) children.

Z-Scores corresponded to the worldwide reference values in all studied age groups at baseline. Global lung function was not affected by exercise, only the youngest group exhibited higher FVC and lower FEF₇₅ , FEV₁ /FVC attributable to the training effect. The overall degree of ventilation heterogeneity assessed by CV showed no exercise dependency. The histograms of pixel values of FEV₁ /FVC, t₅₀ , and t₇₅ revealed a slight modulating effect of exercise on regional ventilation distribution in all subgroups. EIT identified the distinctly higher ventilation heterogeneity in the CF children.

Global and regional lung functions were not affected by exercise in lung-healthy children. Exercise did not increase ventilation inhomogeneity. The obtained EIT-derived regional lung parameters can serve as reference values for future studies in children with lung diseases.