胎羊缺氧时心率变异的功率谱分析

Power Spectral Analysis on Heart Rate Variability of Hypoxaemia in Fetal Lambs

健康妊娠绵羊 7只 ,体重 2 0～ 30 kg,于妊娠 116～ 12 5 d时进宫腔行胎羊股动脉插管 ,引出腹主动脉血压 ,经磁带数据记录仪记录血压信号。术后恢复 1h,从胎羊动脉导管注入明胶微球悬浮液 ,造成胎盘微血管阻塞 ,每隔 15～ 2 0 m in注入一次 ,造成胎羊缺氧。采集胎羊动脉血样 ,分析 p H、Pco2 和 Po2 值 ,同时功率谱分析从血压中检测的拍 -拍心搏周期。频率分成四个频段 ,极低频段 (VL 0 .0 1～ 0 .0 2 5 cycle/ beat) ,低频段 (L 0 .0 2 5～ 0 .12 5 cycle/beat) ,中频段 (M0 .12 5～ 0 .2 cycle/ beat)和高频段 (H0 .2～ 0 .5 cycle/ beat)。结果显示低频段面积在微球注入一次后有极明显增加 ,0 .0 7± 0 .0 1vs.0 .2 1± 0 .0 3(P<0 .0 1) ,增加约 2倍 ;高频段面积有明显下降 ,0 .5 3± 0 .1vs.0 .2 7±0 .0 5 (P<0 .0 5 ) ,下降约 1倍 (P<0 .0 5 ) ;极低频和中频变化无显著性差异。而 p H、Pco2 和 Po2 值在注入 2或 3次后才有明显改变 (P<0 .0 5 )。提示低频和高频段的变化是一较灵敏的胎羊缺氧指标。

To analyze the effect of hypoxaemia on heart rate variability(HRV) in fetal lambs by means of power spectrum,the intrauterine surgical operations were performed at 116~125 gestational days in 7 lambs. Arterial catheter was inserted in the fetal femoral artery and sent to aorta abdominalis,and blood pressure was recorded continually on tape recorder. The microspheres were injected via the arterial catheter to block the micrangium of placenta,thus making an animal model of fetal hypoxaemia. The fetal blood sample was drawn through the catheter for blood gas analysis. In terms of the heart beat variability power spectral density,there were four consistent components,namely very low(VL,0.01~0.025cycle/beat),low(L,0.025~0.125cycle/beat),middle(M,0.125~0.2cycle/beat),and high(H,0.2~0.5cycle/beat). Integrated peaks in the power spectrum were compared before and after administration of microsphere. The spectral power in the L frequency components was significantly increased(0.07±0.01vs.0.21±0.03,P<0.01),and the spectral power in the H frequency components was significantly reduced(0.53±0.1vs.0.27±0.05,P<0.05). There was no significant difference in M and VL. The times of microsphere injection were related to fetal blood pH(r=0.585,p<0.01),Pco 2(r=0.5,p<0.05) and Po 2(r=0.75,P<0.01). The results clearly demonstrate the association between change of power spectrum of heart rate variability and the effect of hypoxia of the fetus in labour.