Parker Kim H
Department of Bioengineering, Imperial College, London, UK.
Med Biol Eng Comput. 2009 Feb;47(2):175-88. doi: 10.1007/s11517-009-0439-y. Epub 2009 Feb 11.
Wave intensity analysis applies methods first used to study gas dynamics to cardiovascular haemodynamics. It is based on the method of characteristics solution of the 1-D equations derived from the conservation of mass and momentum in elastic vessels. The measured waveforms of pressure P and velocity U are described as the summation of successive wavefronts that propagate forward and backward through the vessels with magnitudes dP (+/-) and dU (+/-). The net wave intensity dPdU is the flux of energy per unit area carried by the wavefronts. It is positive for forward waves and negative for backward waves, providing a convenient tool for quantifying the timing, direction and magnitude of waves. Two methods, the PU-loop and the sum of squares, are given for calculating the wave speed c from simultaneous measurements of P and U at a single location. Given c, it is possible to separate the waveforms into their forward and backward components. Finally, the reservoir-wave hypothesis that the arterial and venous pressure can be conveniently thought of as the sum of a reservoir pressure arising from the total compliance of the vessels (the Windkessel effect) and the pressure associated with the waves is discussed.
波强度分析将最初用于研究气体动力学的方法应用于心血管血液动力学。它基于从弹性血管中的质量和动量守恒推导出来的一维方程的特征线解法。测得的压力P和速度U的波形被描述为连续波前的总和，这些波前以大小为dP(+/-)和dU(+/-)的幅度在血管中向前和向后传播。净波强度dPdU是波前携带的单位面积能量通量。对于向前波为正，对于向后波为负，为量化波的时间、方向和幅度提供了一个方便的工具。给出了两种从单个位置同时测量P和U来计算波速c的方法，即PU环法和平方和法。已知c后，就可以将波形分离为向前和向后的分量。最后，讨论了血管库波假说，即动脉压和静脉压可以方便地看作是由血管总顺应性产生的库压力（风箱效应）与与波相关的压力之和。
