Effect of maternal oxygen supplementation by high-flow nasal oxygen compared with room air on fetal acidemia：study protocol for a randomized controlled trial

Abstract Background：Maternal oxygen supplementation is usually used as an intrauterine resuscitation technique to prevent fetal hypoxia and acidemia during delivery. However, there has been a great deal of controversy about the effects of prophylactic maternal oxygen during cesarean section, during which the incidence of fetal acidemia is seemly higher compared with labor. The high-flow nasal oxygen(HFNO) can improve the patients’ oxygenation better, with high flow oxygen airflow. The purpose of this study is to determine whether maternal oxygen supplementation with HNFO has positive effect on fetal acidemia in cesarean section through umbilical arterial blood gas analysis. Method: This prospective, single-center, randomized, double-blinded trial will enroll 120 patients undergoing cesarean section. Participants will be randomly assigned to HFNO group or air group in a 1:1 allocation. For parturients with HFNO group, the flow rate of 40L/min, heated to 37℃ with humidity 100% oxygen concentration is delivered through the Optiflow high-flow nasal oxygen system. And for air group, the flow rate of 2L/min with air pattern through the same device. The primary outcome was umbilical artery(UA) lactate. Secondary outcomes include UA pH, PO2, PCO2, BE, the incidence of pH<7.20 and pH<7.10, Apgar scores at 1 and 5 minute, the neonatal adverse outcomes. Discussion: Our study is the first trial investigating whether maternal oxygen supplementation with HFNO can reduce the umbilical artery lactate and the incidence of fetal acidemia in cesarean section under combine spinal-epidural anesthesia.