Congenital Diaphragmatic Hernia (CDH) is a diaphragm defect associated with lung hypoplasia and ventilation inhomogeneity (VI). The affected neonates are usually born with respiratory failure and require mechanical ventilation after birth. However, significant interindividual VI differences make ventilation difficult. So far, there are no clinical methods of VI assessment that could be applied to optimize ventilation at the bedside. A new VI index is a ratio of time constants T₁/T₂ of gas flows in both lungs. Pressure-controlled ventilation simulations were conducted using an infant hybrid (numerical-physical) respiratory simulator connected to a ventilator. The parameters of the respiratory system model and ventilator settings were based on retrospective clinical data taken from three neonates (2, 2.6, 3.6 kg) treated in the Paediatric Teaching Clinical Hospital of the Medical University of Warsaw. We searched for relationships between respiratory system impedance (Z) and ventilation parameters: work of breathing (WOB), peak inspiratory pressure (PIP), and mean airway pressure (MAP). The study showed the increased VI described by the T₁/T₂ index value highly correlated with elevated Z, WOB, PIP and MAP (0.8–0.9, the Spearman correlation coefficients were significant at P < 0.001). It indicates that the T₁/T₂ index may help to improve the ventilation therapy of CDH neonates.

We aim to develop a non-invasive, bed-side method for supporting personalised ventilation of neonates with congenital diaphragmatic hernia (CDH). Currently, there are no CDH severity measures to do it. As ventilation inhomogeneity (VI) resulting from lung hypoplasia is highly variable in CDH patients, mechanical ventilation is a real challenge and the risk of lung injury is high. We conducted 250 simulations of conventional ventilation of CDH cases using the infant hybrid (numerical-physical) respiratory simulator and a ventilator. Utilising simulation results, we searched for a regression model describing patient ventilation parameters as a function of the respiratory system parameters, ventilator settings and two new CDH severity measures: VI-degree defined as a ratio of time constants ratio of the contralateral and ipsilateral lung (T1/T2) and chest-wall-to-lung compliance ratio (CW/CL). The regression model aimed to find the T1/T2 and CW/CL values for real CDH cases and estimate optimal, matched to VI-degree, peak inspiratory and mean airway pressure (PIP, MAP). The developed regression models (R2 = 0.78 ÷ 0.98; P < 0.001) enabled to find clinically hard-to-measure values of T1/T2 and CW/CL ratios for three patients, respectively: 9 and 6.52 (P1), 3.5 and 4.96 (P2), and 4 and 5.02 (P3). The T1/T2 and CW/CL correlated with defect size (gamma coefficient: 1; P < 0.05), duration of mechanical ventilation and hospitalization (Spearmen’s coefficient: 0.99; P < 0.01). The clinical and estimated PIP and MAP didn’t differ statistically. The T1/T2 and CW/CL indices can help to personalize CDH infants’ ventilation and might be used for prognostication.