Grönlund J, Bartocci M, Kääpä P, Jahnukainen T, Rautanen M, Halkola L, Välimäki I
Cardiorespiratory Research Unit, University of Turku, Finland.
Med Biol Eng Comput. 1997 Nov;35(6):703-7. doi: 10.1007/BF02510981.
Transcephalic electrical impedance offers a technique for non-invasive, cot-side monitoring of neonatal cerebral circulation but the exact nature of the signal is somewhat ambiguous. The impedance signal is examined in an animal project where the ventilator settings are adjusted (20 min-1-10 min-1-40 min-1 for 10 min periods each) to produce circulatory changes. Six juvenile pigs are intubated, and ECG, arterial blood pressure, carotid flow (CF) by electromagnetic flowmeter and impedance are continuously monitored and stored on analogue tape. Cardiac output by thermodilution, blood oxygen (pO2) and carbon dioxide (pCO2) tensions are measured. ECG is converted to heart rate, mean blood pressure is integrated, and the high-frequency (1.50-4.00 Hz) component of the impedance signal delta Z is computed using autoregressive spectral estimation. Stroke volume, peripheral vascular resistance (PVR) and cerebral vascular resistance (CVR) are calculated. pCO2 and CF increase and pO2 decreases during hypoventilation. CF correlates positively with cardiac output, stroke volume, delta Z and pCO2, and negatively with pO2 and CVR. delta Z correlates positively with heart rate and cardiac output, and negatively with PVR and CVR. It is concluded that the impedance signal is related to the amount of blood transmitted to the brain by every beat of the heart, depending on the changes in both the systemic circulation and the cerebral vascular compliance.
经颅电阻抗提供了一种用于新生儿脑循环无创床边监测的技术，但信号的确切性质有些模糊。在一个动物实验项目中对阻抗信号进行了检测，在该项目中调整呼吸机设置（每次10分钟，分别为20次/分钟 - 10次/分钟 - 40次/分钟）以产生循环变化。对六只幼年猪进行插管，并持续监测心电图、动脉血压、通过电磁流量计测量的颈动脉血流（CF）和阻抗，并存储在模拟磁带上。通过热稀释法测量心输出量、血氧（pO2）和二氧化碳（pCO2）张力。将心电图转换为心率，对平均血压进行积分，并使用自回归谱估计计算阻抗信号增量Z的高频（1.50 - 4.00 Hz）分量。计算每搏输出量、外周血管阻力（PVR）和脑血管阻力（CVR）。通气不足时pCO2和CF升高，pO2降低。CF与心输出量、每搏输出量、增量Z和pCO2呈正相关，与pO2和CVR呈负相关。增量Z与心率和心输出量呈正相关，与PVR和CVR呈负相关。得出的结论是，阻抗信号与心脏每次搏动传输到大脑的血量有关，这取决于体循环和脑血管顺应性的变化。
