LAUSR

OBJECTIVE  Delayed cord clamping (DCC) and 21 to 30% O2 resuscitation is recommended for preterm infants but is commonly associated with low pulmonary blood flow (Qp) and hypoxia. 100% O2 supplementation during DCC for 60 seconds followed by 30% O2 may increase Qp and oxygen saturation (SpO2). STUDY DESIGN  Preterm lambs (125-127 days of gestation) were resuscitated with 100% O2 with immediate cord clamping (ICC, n = 7) or ICC + 30% O2, and titrated to target SpO2 (n = 7) or DCC + 100% O2 for 60 seconds, which followed by cord clamping and 30% O2 titration (n = 7). Seven preterm (23-27 weeks of gestation) human infants received continuous positive airway pressure (CPAP) + 100% O2 for 60 seconds during DCC, cord clamping, and 30% O2 supplementation after cord clamping. RESULTS  Preterm lambs in the ICC + 100% O2 group resulted in PaO2 (77 ± 25 mmHg), SpO2 (77 ± 11%), and Qp (27 ± 9 mL/kg/min) at 60 seconds. ICC + 30% O2 led to low Qp (14 ± 3 mL/kg/min), low SpO2 (43 ± 26%), and PaO2 (19 ± 7 mmHg). DCC + 100% O2 led to similar Qp (28 ± 6 mL/kg/min) as ICC + 100% O2 with lower PaO2. In human infants, DCC + CPAP with 100% O2 for 60 seconds, which followed by weaning to 30% resulted in SpO2 of 92 ± 11% with all infants >80% at 5 minutes with 100% survival without severe intraventricular hemorrhage. CONCLUSION  DCC + 100% O2 for 60 seconds increased Qp probably due to transient alveolar hyperoxia with systemic normoxia due to "dilution" by umbilical venous return. Larger translational and clinical studies are warranted to confirm these findings. KEY POINTS · Transient alveolar hyperoxia during delayed cord clamping can enhance pulmonary vasodilation.. · Placental transfusion buffers systemic oxygen tension and limits hyperoxia.. · Use of 100% oxygen for 60 seconds during DCC was associated with SpO2 ≥80% by 5 minutes..