New insights in respiratory impedance in young children after repair of congenital diaphragmatic hernia: a cross-sectional study

Lung function impairment is common in Congenital Diaphragmatic Hernia (CDH) survivors. The aim of this study was to evaluate, in children who underwent CDH surgical repair, mid and long-term consequences on respiratory impedance, investigating the impact of CDH on both resistance and reactance parameters, as well as bronchodilator response. Forced Oscillation Technique (FOT) parameters were collected from 12 patients (2-11 years). Resistance and reactance values at 8 Hz (Rrs8, Xrs8) and the area under the reactance curve (AX) were measured pre and post-salbutamol. Quantitative variables were compared using Mann-Whitney U test. Differences of categorical variables were evaluated using Fisher exact test. Statistically significant differences between measured and predicted values for Rrs8 (p = 0.04), Xrs8 (p = 0.02) and AX (p = 0.01) were found. When stratifying for age, significant difference between measured and predicted values was observed only in children < 5 years (n = 6) (Rrs8 p = 0.03, Xrs8 p = 0.001, AX p = 0.007). With respect to children 5 years (n = 6), the younger ones showed higher z-scores in Rrs8 (p = 0.015), Xrs8 (p = 0.002) and AX (p = 0.002) values. Since the z-score difference was greater than 0.5, it was considered a difference clinically relevant. No differences in bronchodilator response were recorded. In children with CDH an impairment of respiratory impedance measured by FOT is observed only in children aged less than 5 years.