Ventilation-to-perfusion relationships and right-to-left shunt during neonatal intensive care in infants with congenital diaphragmatic hernia

BACKGROUND: We aimed to explore the postnatal evolution of ventilation/perfusion ratio (V(A)/Q) and right-to-left shunt in infants with congenital diaphragmatic hernia (CDH) and whether these indices predicted survival to discharge. METHODS: Retrospective cohort study at King’s College Hospital, London, UK of infants admitted with CDH in 10 years (2011–2021). The non-invasive method of the oxyhaemoglobin dissociation curve was used to determine the V(A)/Q and shunt in the first 24 h of life, pre-operation, pre-extubation and in the deceased infants, before death. RESULTS: Eighty-two infants with CDH (71 left-sided) were included with a median (IQR) gestation of 38.1(34.8–39.0) weeks. Fifty-three (65%) survived to discharge from neonatal care. The median (IQR) V(A)/Q in the first 24 h was lower in the deceased infants [0.09(0.07–0.12)] compared to the ones who survived [0.28(0.19–0.38), p < 0.001]. In the infants who survived, the V(A)/Q was lower in the first 24 h [0.28 (0.19–0.38)] compared to pre-operation [0.41 (0.3–0.49), p < 0.001] and lower pre-operation compared to pre-extubation [0.48 (0.39–0.55), p = 0.027]. The shunt was not different in infants who survived compared to the infants who did not. CONCLUSIONS: Ventilation-to-perfusion ratio was lower in infants who died in the neonatal period compared to the ones that survived and improved in surviving infants over the immediate postnatal period. IMPACT: The non-invasive method of the oxyhaemoglobin dissociation curve was used to determine the ventilation/perfusion ratio V(A)/Q in infants with congenital diaphragmatic hernia (CDH) in the first 24 h of life, pre-operation, pre-extubation and in the deceased infants, before death. The V(A)/Q in the first 24 h of life was lower in the infants who did not survive to discharge from neonatal care compared to the ones who survived. In the infants who survived, the V(A)/Q improved over the immediate postnatal period. The non-invasive calculation of V(A)/Q can provide valuable information relating to survival to discharge.