Kawamoto M, Sera A, Kaneko K, Yuge O, Ohtani M
Department of Anesthesiology and Critical Care, Hiroshima University Hospital, Japan.
Acta Anaesthesiol Scand. 1998 Jan;42(1):47-51. doi: 10.1111/j.1399-6576.1998.tb05079.x.
Power spectral analysis of heart rate variability is a useful monitoring of brain-damaged patients. However, the effect of artificial ventilation is not clearly demonstrated in assessing vagal activity because the locus of its activity is originated close to the respiratory center in the brain stem. We studied heart rate variability during artificial ventilation and apnea test as part of an assessment of brain death.
Ten adult patients with severe brain damage were studied. Power spectral analysis of heart rate variability from electrocardiographic R-R intervals was integrated to compare spectral components before, during and after the apnea test. Before the test, circulatory and blood gas variables and electrocardiographic recording were obtained under controlled mechanical ventilation at a rate of 12 and 18 (/min), each for 5 min. Measurements were made for 10 min during the apnea test, and repeated thereafter as before the test. Power spectral analysis based on fast Fourier transformation was made by integrating each low- (LF: 0.04-0.15 Hz) and high- (HF: 0.15-0.40 Hz) frequency band areas. LF was assessed as sympathetic and parasympathetic nervous activity, and HF as respiratory-related parasympathetic vagal activity. The HF/LF ratio showed sympathovagal balance.
All patients were assessed as brain dead. During apnea, PaCO2 (P<0.01) and LF (P<0.05) increased, and pH (P<0.01) and HF/LF ratio (P<0.05) decreased. Heart rate, mean arterial pressure, PaO2 and HF remained consistent throughout.
It was shown that sympathovagal balance was inclined to be sympathotonic during apnea, and that there were no changes in the respiratory-related vagal activity in spite of stopping artificial ventilation.
心率变异性的功率谱分析是监测脑损伤患者的一种有用方法。然而，人工通气对评估迷走神经活动的影响尚未明确显现，因为其活动位点起源于脑干呼吸中枢附近。作为脑死亡评估的一部分，我们研究了人工通气和 apnea 试验期间的心率变异性。
对 10 名严重脑损伤的成年患者进行了研究。通过整合心电图 R-R 间期的心率变异性功率谱分析，比较 apnea 试验前、试验期间和试验后的频谱成分。试验前，在控制机械通气下，以 12 次/分钟和 18 次/分钟的频率分别获取循环和血气变量以及心电图记录，各持续 5 分钟。在 apnea 试验期间进行 10 分钟测量，并在试验后如试验前一样重复测量。基于快速傅里叶变换的功率谱分析通过整合每个低频（LF：0.04 - 0.15Hz）和高频（HF：0.15 - 0.40Hz）频段面积进行。LF 被评估为交感和副交感神经活动，HF 为呼吸相关的副交感迷走神经活动。HF/LF 比值显示交感迷走神经平衡。
所有患者均被评估为脑死亡。在 apnea 期间，PaCO2（P<0.01）和 LF（P<0.05）升高，pH（P<0.01）和 HF/LF 比值（P<0.05）降低。心率、平均动脉压、PaO2 和 HF 始终保持一致。
结果表明，在 apnea 期间交感迷走神经平衡倾向于交感神经占优势，并且尽管停止了人工通气，呼吸相关的迷走神经活动没有变化。
