Frequency dependence of cerebrovascular impedance in preterm neonates: A different view on critical closing pressure
Frequency dependence of cerebrovascular impedance in preterm neonates: A different view on critical closing pressure
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DOI：
10.1097/00004647-199710000-00015
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发表时间：
1997-10-01
影响因子：
6.3
通讯作者：
Jorch, G
中科院分区：
文献类型：
--
作者：
Michel, E;Hillebrand, S;Jorch, G
用临界关闭压(CCP)的概念很好地解释了瞬时动脉压(BP)和脑血流速度(CBFv)之间的非比例关系。我们的目的是测定新生儿脑血管系统的频率响应，并建立生理条件下脑血管阻抗与CCP之间的精确数学关系。对10例早产儿(胎龄25~32周；出生体重685~1730g；出生1~7日龄)进行颈内动脉血流频谱多普勒描记。同时测量血压。用图形确定了临界关闭压力。脑血管阻抗计算为零频率、心率(H)和谐波(XH)时BP和CBFv功率谱中相应峰值之比的平方根。与零频率下的阻抗相比，H~3H(2~6赫兹)之间的阻抗均匀地减小了约5倍。脑血管系统的行为就像一个高通滤波器，导致CBFv(类似于电流)的DC(直流)分量相对于驱动力BP(类似于电压)的DC(直流)分量减少。脑血管阻抗的频率响应反映了CCP和DC BP的比值。给出了与观测结果相匹配的关系的数学推导，从而证明了CCP方法和阻抗方法的有效性。
The nonproportional relationship between instantaneous arterial blood pressure (BP) and cerebral blood flow velocity (CBFv) is well explained by the concept of critical closing pressure (CCP). We aimed to determine the frequency response of the neonatal cerebrovascular system, and to establish the exact mathematical relationship between cerebrovascular impedance and CCP under physiologic conditions. In 10 preterm neonates (gestational age, 25-32 weeks; birth weight, 685-1,730 g; age 1-7 days) we Doppler-traced CBFv of the internal carotid artery. Blood pressure was traced simultaneously. Critical closing pressure was graphically determined. Cerebrovascular impedance was calculated as the square root of the ratio of the corresponding peaks in the power spectra of BP and CBFv at zero frequency, and at heart rate (H) and harmonics (xH). Uniformly, the impedance between H and 3H (2 to 6 Hz) was reduced about fivefold, compared with the impedance at zero frequency. The cerebrovascular system behaves like a high-pass filter, leading to a reduction of the DC (direct current) component of CBFv (analogous to current) relative to that of the driving force BP (analogous to voltage). The frequency response of cerebrovascular impedance reflects the ratio of CCP and DC BP. A mathematical derivation of this relationship is given matching the observed results, Thus, both the CCP and the impedance approach are valid.