Supplementary Material for: Bioreactance Cardiac Output Trending Ability in Preterm Infants: A Single Centre, Longitudinal Study

<b><i>Introduction:</i></b> It is unknown whether bioreactance (BR) can accurately track cardiac output (CO) changes in preterm neonates. <b><i>Methods:</i></b> A prospective observational longitudinal study was performed in stable preterm infants (&lt;37 weeks) during the first 72 h of life. Stroke volume (SV) and CO, as measured by BR and transthoracic echocardiography, were compared. <b><i>Results:</i></b> The mean gestational age (GA) was 31.3 weeks and mean birth weight (BW) was 1,563 g. Overall, 690 measurements were analysed for trending ability by 4-quadrant and polar plots. For non-weight-indexed measurements, 377 (54.6%) lay outside the 5% exclusion zone, the concordance rate was poor (77.2%) with a high mean angular bias (28.6°), wide limits of agreement and a poor angular concordance rate (17.4%). Neither GA, BW nor respiratory support mode affected trending data. Patent ductus arteriosus, postnatal age, and CO level had variable effects on trending data. Trending data for 5 and 10% exclusion zones were also compared. <b><i>Conclusion:</i></b> The ability of BR to track changes in CO is not interchangeable with CO changes as measured by echocardiography. BR, as a trend monitor for changes in CO or SV to determine clinical decisions around interventions in neonatology, should be used with caution.

<b><i>引言：</i></b> 目前尚不清楚生物反应度（bioreactance, BR）能否精准追踪早产新生儿的心输出量（cardiac output, CO）变化。
<b><i>方法：</i></b> 本研究针对胎龄小于37周的稳定早产婴儿，在其出生后前72小时内开展前瞻性观察性纵向研究，对比通过生物反应度（BR）与经胸超声心动图测得的每搏输出量（stroke volume, SV）及心输出量（CO）。
<b><i>结果：</i></b> 本研究纳入对象的平均胎龄（gestational age, GA）为31.3周，平均出生体重（birth weight, BW）为1563 g。最终共对690次测量数据进行分析，通过四象限图与极坐标图评估其趋势追踪能力。针对未进行体重标化的测量数据，有377次（54.6%）落在5%排除区外，一致性率较差（77.2%），同时伴随较高的平均角度偏倚（28.6°）、较宽的一致性界限，且角度一致性率较低（17.4%）。胎龄、出生体重及呼吸支持模式均未对趋势追踪数据产生影响；动脉导管未闭、出生后年龄及心输出量水平则对趋势追踪数据存在不同程度的影响。本研究还对比了5%与10%排除区对应的趋势追踪数据。
<b><i>结论：</i></b> 生物反应度（BR）追踪心输出量变化的能力，与超声心动图测得的心输出量变化并不具有互换性。在新生儿科临床实践中，若将生物反应度作为追踪心输出量或每搏输出量变化以指导干预决策的趋势监测手段，应谨慎使用。