Shakespeare S A, Crowe J A, Hayes-Gill B R, Bhogal K, James D K
School of Electrical and Electronic Engineering, University of Nottingham, UK.
Med Biol Eng Comput. 2001 Nov;39(6):619-26. doi: 10.1007/BF02345432.
Knowledge of the content of Doppler ultrasound signals from the fetal heart is essential if the performance of fetal heart rate (FHR) monitors based upon this technology is to be improved. For this reason instrumentation was constructed to enable the simultaneous collection of Doppler audio signals and the transabdominal fetal ECG (for signal registration), with a total of 22 recordings being made with an average length of around 20 minutes. These data demonstrate the transient nature of the Doppler audio data with wide variations in the signal content observable on a beat-to-beat basis. Short-time Fourier analysis enabled the content of the Doppler signals to be linked to six cardiac events, four valve and two wall motions, with higher frequency components being associated with the latter. This differing frequency content together with information regarding the direction of movement that can be discerned from Doppler signals provided a potential means of discriminating between these six events (which are unlikely to all contribute to the Doppler signal within the same cardiac cycle). Analysis of 100 records showed that wall contractions generate the most prominent signals, with atrial contraction recognisable in all records and ventricular wall contraction in 95% (although its amplitude is only around 30% of that of the atrial signal). Valve motion, with amplitudes between 15 and 25% that of the atrial wall signal, were visible in 75% of records. These results suggest means by which the six events that contribute to the Doppler signal may be distinguished, providing information that should enable an improvement in the current performance of Doppler ultrasound-based FHR monitors.
如果要改进基于这项技术的胎儿心率（FHR）监测仪的性能，了解来自胎儿心脏的多普勒超声信号内容至关重要。因此，构建了一种仪器，能够同时采集多普勒音频信号和经腹胎儿心电图（用于信号记录），共进行了22次记录，平均时长约为20分钟。这些数据证明了多普勒音频数据的瞬态特性，逐搏观察到的信号内容存在很大差异。短时傅里叶分析使多普勒信号的内容能够与六个心脏事件、四个瓣膜和两个壁运动相关联，高频成分与后者相关。这种不同的频率内容以及从多普勒信号中可辨别出的运动方向信息，提供了一种区分这六个事件的潜在方法（在同一个心动周期内，它们不太可能都对多普勒信号有贡献）。对100份记录的分析表明，壁收缩产生的信号最为突出，所有记录中均可识别心房收缩，95%的记录中可识别心室壁收缩（尽管其幅度仅约为心房信号的30%）。瓣膜运动的幅度在心房壁信号的15%至25%之间，在75%的记录中可见。这些结果表明了区分对多普勒信号有贡献的六个事件的方法，提供的信息应能改善当前基于多普勒超声的FHR监测仪的性能。
