Objective Lung hypoplasia associated with congenital diaphragmatic hernia (CDH) results in respiratory insufficiency and pulmonary hypertension after birth. We have investigated whether aerating the lung before removing placental support (physiologically based cord clamping (PBCC)), improves the cardiopulmonary transition in lambs with a CDH.
Methods At ≈138 days of gestational age, 17 lambs with surgically induced left-sided diaphragmatic hernia (≈d80) were delivered via caesarean section. The umbilical cord was clamped either immediately prior to ventilation onset (immediate cord clamping (ICC); n=6) or after achieving a target tidal volume of 4 mL/kg, with a maximum delay of 10 min (PBCC; n=11). Lambs were ventilated for 120 min and physiological changes recorded.
Results Pulmonary blood flow (PBF) increased following ventilation onset in both groups, but was 19-fold greater in PBCC compared with ICC lambs at cord clamping (19±6.3 vs 1.0±0.5 mL/min/kg, p<0.001). Cerebral tissue oxygenation was higher in PBCC than ICC lambs during the first 10 min after cord clamping (59%±4% vs 30%±5%, p<0.001). PBF was threefold higher (23±4 vs 8±2 mL/min/kg, p=0.01) and pulmonary vascular resistance (PVR) was threefold lower (0.6±0.1 vs 2.2±0.6 mm Hg/(mL/min), p<0.001) in PBCC lambs compared with ICC lambs at 120 min after ventilation onset.
Conclusions Compared with ICC, PBCC prevented the severe asphyxia immediately after birth and resulted in a higher PBF due to a lower PVR, which persisted for at least 120 min after birth in CDH lambs.
- congenital diaphragmatic hernia
- neonatal transition
- perinatal care
- pulmonary hypertension
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Contributors All authors included in this paper fulfill the criteria of authorship, specifically: PLJD, AJK, RJH, KJC, MT and SBH designed the experiments. AJK, KJC, MT, KAR, BJA, EVM, PLJD and SBH were essential for undertaking the experiments. AJK, PLJD, KJC and SBH were responsible for data analysis. AJK wrote the first draft of the manuscript; PLJD and KJC provided initial critical feedback. All authors contributed by modifying and editing the manuscript and all approved final version.
Funding This research project was funded by grants from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) Foundation, Cabrini Foundation, CDH Australia and the Victorian Government’s Operational Infrastructure Support Program.
Disclaimer The funders were not involved in the study design; in the collection, analysis and interpretation of the data; in the writing of the report or in the decision to submit the paper for publication.
Competing interests None declared.
Ethics approval All procedures in animals were approved by the animal ethics committee at Monash University.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Not required.
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