Quick Christopher M, Berger David S, Noordergraaf Abraham
Center for Cerebrovascular Research, University of California, San Francisco 94110, USA.
IEEE Trans Biomed Eng. 2002 May;49(5):440-5. doi: 10.1109/10.995682.
Traditionally, input impedance (Z(in)) has been used to characterize the global dynamic properties of an arterial system independent of properties of the heart. Defined as the relationship of pressure and flow at the entrance of an arterial system, it describes the ability of an arterial system to dynamically impede blood flow. Recently, a new description has been developed that also characterizes the arterial system independent of properties of the heart. Apparent arterial compliance (C(app)) is defined as the dynamic relationship of input pressure and volume stored in an arterial system, and describes the ability of the arterial system to dynamically store blood. Both Z(in) and C(app) are influenced by pulse wave propagation and reflection. However, the functional form of Capp lends itself to describing the arterial system in terms of negative feedback. Pulse wave reflection decreases the pulsatile volume stored (gain) at low frequencies, but increases the range of frequencies (bandwidth) in which the pulsatile volume is determined by total arterial compliance. This paper illustrates, by simple analytical formula, large-scale arterial system modeling, and direct analysis of data, how this conceptualization of reflection offers a new means to interpret changes in arterial system dynamics resulting from changes in arterial compliance.
传统上，输入阻抗（Z(in)）已被用于表征独立于心脏特性的动脉系统的整体动态特性。它被定义为动脉系统入口处压力与流量的关系，描述了动脉系统动态阻碍血流的能力。最近，一种新的描述方法也已被开发出来，它同样可以独立于心脏特性来表征动脉系统。表观动脉顺应性（C(app)）被定义为输入压力与动脉系统中储存的容积之间的动态关系，并描述了动脉系统动态储存血液的能力。Z(in)和C(app)都受脉搏波传播和反射的影响。然而，Capp的函数形式有助于用负反馈来描述动脉系统。脉搏波反射在低频时会减少储存的脉动容积（增益），但会增加脉动容积由总动脉顺应性决定的频率范围（带宽）。本文通过简单的解析公式、大规模动脉系统建模以及对数据的直接分析，阐述了这种反射概念如何提供一种新方法来解释由于动脉顺应性变化而导致的动脉系统动力学变化。
