Archives of Disease in Childhood - Fetal and Neonatal Edition | 2021
Effect of breathing on venous return during delayed cord clamping: an observational study
Abstract
Objective To investigate the effect of spontaneous breathing on venous return in term infants during delayed cord clamping at birth. Methods Echocardiographic ultrasound recordings were obtained directly after birth in healthy term-born infants. A subcostal view was used to obtain an optimal view of the inferior vena cava (IVC) entering the right atrium, including both the ductus venosus (DV) and the hepatic vein (HV). Colour Doppler was used to assess flow direction and flow velocity. Recordings continued until the umbilical cord was clamped and were stored in digital format for offline analyses. Results Ultrasound recordings were obtained in 15 infants, with a median (IQR) gestational age of 39.6 (39.0–40.9) weeks and a birth weight of 3560 (3195–4205) g. Flow was observed to be antegrade in the DV and HV in 98% and 82% of inspirations, respectively, with flow velocity increasing in 74% of inspirations. Retrograde flow in the DV was observed sporadically and only occurred during expiration. Collapse of the IVC occurred during 58% of inspirations and all occurred caudal to the DV inlet (100%). Conclusion Spontaneous breathing was associated with collapse of the IVC and increased antegrade DV and HV flow velocity during inspiration. Therefore, inspiration appears to preferentially direct blood flow from the DV into the right atrium. This indicates that inspiration could be a factor driving placental transfusion in infants. Real-time echocardiographic monitoring of blood flow in the ductus venosus and hepatic vein was undertaken during perinatal transition with intact umbilical cord of term born infants. Antegrade flow increased during inspiration, preferentially directing blood flow from the ductus venosus into the right atrium.