Supplementary Material for: Reference values of cerebral fractional tissue oxygen extraction (cFTOE) in preterm neonates during immediate fetal-to-neonatal transition: A secondary outcome analysis of the COSGOD III trial

Background
Monitoring cerebral oxygenation during immediate fetal-to-neonatal transition may provide additional information in preterm neonates. Cerebral fractional tissue oxygen extraction (cFTOE), derived from cerebral oxygen saturation (crSO2) and arterial oxygen saturation (SpO2), reflects the relative extraction of oxygen from the arterial to the tissue compartment, providing information about the balance between oxygen delivery and oxygen consumption. We aimed to describe centiles of cFTOE during the first 15 minutes after birth in extremely and very preterm neonates.

Methods
This is a secondary outcome parameter analysis of the multicentre randomised-controlled COSGOD III trial. Neonates <32 weeks of gestational age included in the NIRS-open-group of the COSGOD III trial with favourable outcome, defined as survival without cerebral injury at term-equivalent age, were assigned for this analysis. CFTOE was calculated for every minute in each included neonate: cFTOE = (SpO2-crSO2)/SpO2. CrSO2 was measured with the INVOS 5100 monitor with the neonatal sensor. Centiles of cFTOE (10th to 90th) from minute two to 15 after birth were described.

Results
A total of 199 preterm neonates with a median (IQR) gestational age of 29.7 (27.7-30.9)weeks and a weight of 1200 (925-1460)grams were analysed. The 50th centile of cFTOE at minute two, five, ten and 15 was 0.492, 0.296, 0.177 and 0.151, respectively.

Conclusion
This study provides centile for cFTOE for extremely and very preterm neonates with favourable outcome independent of interventions during postnatal stabilisation period. These centile charts may assist in interpreting cerebral oxygenation patterns.

背景
在胎儿至新生儿即刻过渡期监测脑氧合，或可为早产儿提供额外临床参考信息。脑局部组织氧摄取分数（cerebral fractional tissue oxygen extraction, cFTOE）由脑氧饱和度（cerebral oxygen saturation, crSO2）与动脉血氧饱和度（arterial oxygen saturation, SpO2）计算得出，可反映氧从动脉向组织间隙的相对摄取量，体现氧输送与氧消耗之间的平衡状态。本研究旨在描述极早早产儿与非常早产儿出生后最初15分钟内的cFTOE百分位数分布。

方法
本研究为多中心随机对照COSGOD Ⅲ试验的次要结局参数分析。纳入COSGOD Ⅲ试验近红外光谱开放组中胎龄<32周、且结局良好的新生儿（定义为校正胎龄时存活且无脑损伤）进行本次分析。对每例纳入新生儿的每分钟cFTOE进行计算：cFTOE = (SpO2 - crSO2)/SpO2。采用搭载新生儿传感器的INVOS 5100监护仪测量crSO2。本研究描述了出生后第2分钟至第15分钟的cFTOE百分位数（第10至第90百分位）。

结果
本研究共分析199例早产儿，其中位（四分位数间距）胎龄为29.7（27.7~30.9）周，体重为1200（925~1460）g。出生后第2、5、10、15分钟的cFTOE第50百分位数分别为0.492、0.296、0.177和0.151。

结论
本研究提供了结局良好的极早早产儿与非常早产儿的cFTOE百分位数参考值，且该参考值不受产后稳定期干预措施的影响。上述百分位数图表可辅助临床医师解读脑氧合模式。