Supplementary Material for: Analysis of fractional cerebral oxygen extraction in preterm infants during the kangaroo care.

Introduction: We aimed to investigate the cerebral fractional tissue oxygen extraction (FtOE) during kangaroo care (KC) in premature infants and compare cardiorespiratory stability and hypoxic or bradycardic events between KC and incubator care.
Methods: A single center prospective observational study was carried out at the NICU of a level III perinatal center. Preterm infants < 32 weeks gestational age were subjected to KC. Patients were subjected to continuous monitoring of regional cerebral oxygen saturation (rScO2), peripheral oxygen saturation (SpO2), and heart rate (HR) during KC, before KC (pre-KC), and after KC (post-KC). The monitoring data were stored and exported to MATLAB for synchronization and signal analysis including the calculation of the FtOE and events analysis (i.e., desaturations and bradycardias counts and anormal values). Furthermore, the event counts and the mean SpO2, HR, rScO2, and FtOE were compared between studied periods employing the Wilcoxon rank-sum test and the Friedman test, respectively.
Results: A total of forty-three KC sessions with their corresponding pre-KC and post-KC segments were analyzed. The distributions of the SpO2, HR, rScO2, and FtOE showed different patterns according to the respiratory support, but not differences between the studied periods were detected. Accordingly, no significant differences in monitoring events were evidenced. However, cerebral metabolic demand (FtOE) was significantly lower during KC compared with post-KC (p=0.019).
Discussion/Conclusion: Premature infants remain clinically stable during KC. Moreover, cerebral oxygenation is significantly higher and cerebral tissular oxygen extraction is significantly lower during KC compared with incubator care in post-KC. No differences in HR and SpO2 were shown. This novel data analysis methodology could be expanded to other clinical situations.

引言：本研究旨在探究早产儿袋鼠式护理（Kangaroo Care, KC）期间的脑区域组织氧摄取分数（cerebral fractional tissue oxygen extraction, FtOE），并对比袋鼠式护理与暖箱护理的心肺稳定性及低氧、心动过缓事件发生情况。方法：本研究为一项单中心前瞻性观察性研究，于某三级围产中心的新生儿重症监护病房（Neonatal Intensive Care Unit, NICU）开展。纳入胎龄小于32周的早产儿实施袋鼠式护理。在袋鼠式护理期间、护理前（pre-KC）及护理后（post-KC）三个阶段，对受试者的区域脑氧饱和度（regional cerebral oxygen saturation, rScO2）、脉搏血氧饱和度（peripheral oxygen saturation, SpO2）及心率（heart rate, HR）进行持续监测。将监测数据存储并导出至MATLAB软件，进行数据同步与信号分析，包括脑区域组织氧摄取分数（FtOE）的计算以及事件分析（即血氧下降与心动过缓事件的计数与异常值判定）。此外，分别采用Wilcoxon秩和检验对比事件计数，采用Friedman检验对比各研究阶段的平均SpO2、HR、rScO2及FtOE水平。结果：本研究共分析了43次袋鼠式护理疗程及其对应的护理前与护理后阶段数据。SpO2、HR、rScO2及FtOE的分布特征随呼吸支持方式不同而存在差异，但各研究阶段间未检测到显著差异。据此，监测事件未表现出显著统计学差异。不过，与护理后阶段相比，袋鼠式护理期间的脑代谢需求（FtOE）显著降低（p=0.019）。讨论与结论：早产儿在袋鼠式护理期间可维持临床稳态。此外，相较于暖箱护理的护理后阶段，袋鼠式护理期间的脑氧合水平显著更高，脑组织氧摄取分数显著更低。心率与SpO2未表现出显著差异。本研究提出的新型数据分析方法可推广至其他临床场景。