Department of Obstetrics and Gynecology, Tottori University School of Medicine, Yonago, Japan.
J Perinat Med. 2010 Mar;38(2):197-201. doi: 10.1515/jpm.2010.036.
To determine the loss of fetal heart rate (FHR) baseline variability by frequency analysis.
The FHR tracings of 12 normal fetuses and others with various conditions, as well as flat FHR tracings of a late deceleration (LD) and anencephaly recorded with Doppler fetal monitors, were scanned and processed using fast Fourier transform (FFT) analysis. The ratio of the area under the low frequency spectrum divided by the area under the whole spectrum (La/Ta) and the peak power spectrum density (PPSD) were determined.
Long-term variability (LTV) measures >10 bpm revealed significantly more La/Ta and PPSD than LTV <10 bpm in normal FHR tracings. The La/Ta and PPSD were >15% and 60 bpm(2)/Hz, respectively, in representative values of normal FHR cases and in those of fetal respiration, hiccupps and non-reactive FHR, whereas those of the flat baseline of LD and anencephaly were <15% and 60 bpm(2)/Hz.
Loss of baseline variability is diagnosed when the La/Ta ratio and PPSD are <15% and 60 bpm(2)/Hz, respectively, based on the FFT frequency analysis of the FHR baseline.
通过频率分析确定胎儿心率（FHR）基线变异的丧失。
使用快速傅里叶变换（FFT）分析扫描和处理 12 例正常胎儿和其他各种情况的 FHR 迹线以及多普勒胎儿监护仪记录的晚期减速（LD）和无脑畸形的平坦 FHR 迹线。确定低频谱下面积与全谱下面积的比值（La/Ta）和峰值功率谱密度（PPSD）。
长期变异（LTV）测量值>10 bpm 的正常 FHR 迹线的 La/Ta 和 PPSD 明显高于 LTV <10 bpm。正常 FHR 情况下和胎儿呼吸、打嗝和无反应 FHR 的代表性值中，La/Ta 和 PPSD 分别>15%和 60 bpm(2)/Hz，而 LD 和无脑畸形的平坦基线的 La/Ta 和 PPSD 分别<15%和 60 bpm(2)/Hz。
根据 FHR 基线的 FFT 频率分析，当 La/Ta 比值和 PPSD 分别<15%和 60 bpm(2)/Hz 时，诊断为基线变异丧失。
