Bottrich Marcel, Husar Peter
Annu Int Conf IEEE Eng Med Biol Soc. 2018 Jul;2018:5870-5873. doi: 10.1109/EMBC.2018.8513614.
Non-invasive fetal pulse oximetry is the application of reflection pulse oximetry to the abdomen of a pregnant woman. Light sources and detectors areplaced on the belly. Emitted photons travel through maternal and fetal tissue and back to the detectors. The captured photoplethysmogram (PPG) is a complex mixture of the maternal and fetal pulse curve. A purely fetal PPG in time domain is needed to estimate the oxygen level of the unborn child. In this work we describe the application of comb filters to separate the fetalfrom the maternal signal. Finite element simulations and phantom measurements are utilized to generate and measure synthetic signals at different heart rates and noise levels. Comb filters with peak frequencies matched to the fetal heart rate are applied to the mixed PPGs. The filtered signals prove that the extraction of the fetal signal is sufficient even at a distance between the maternal and the fetal signal magnitudes of around 80 dB. The resulting signal quality is sufficient for beat to beat analysis and feature extraction in the time domain. We conclude that comb filtering is a suitable signal separation method for non-invasive fetal pulse oximetry.
无创胎儿脉搏血氧饱和度测定法是将反射式脉搏血氧饱和度测定法应用于孕妇腹部。光源和探测器放置在腹部。发射的光子穿过母体和胎儿组织后返回探测器。捕获的光电容积脉搏波图（PPG）是母体和胎儿脉搏曲线的复杂混合。需要一个时域中的纯胎儿PPG来估计未出生胎儿的氧水平。在这项工作中，我们描述了使用梳状滤波器从母体信号中分离出胎儿信号。利用有限元模拟和模型测量来生成和测量不同心率和噪声水平下的合成信号。将峰值频率与胎儿心率匹配的梳状滤波器应用于混合后的PPG。滤波后的信号表明，即使母体和胎儿信号幅度之间的距离约为80 dB，胎儿信号的提取也是足够的。所得信号质量足以进行逐搏分析和时域中的特征提取。我们得出结论，梳状滤波是一种适用于无创胎儿脉搏血氧饱和度测定法的信号分离方法。
