Pythoud F, Stergiopulos N, Bertram C D, Meister J J
Biomedical Engineering Laboratory, Swiss Federal Institute of Technology, Lausanne, Switzerland.
J Biomech. 1996 Nov;29(11):1419-23. doi: 10.1016/0021-9290(96)84537-4.
In this paper we examine the importance of fluid friction and nonlinearities due to the area-pressure relationship and to the convective acceleration on the separation of arterial pressure and flow waves into their forward and backward components. Experiments were run in straight uniform nonlinearly elastic tubes. Different degrees of fluid friction and nonlinearities, covering the physiological range, have been tested. We predicted the forward and backward running pressure components using two wave separation methods: the classical linear method (Westerhof et al., Cardiovasc. Res, 6,648-656, 1972) and the first order correction (FOC) method (Pythoud et al., Trans ASME J. Biomech. Engng, in press) which takes nonlinearities and fluid friction into account. We found that the two methods yield somewhat different predictions. The differences tend to increase with the degree of fluid friction and nonlinearities and are typically of the order of 4-8%. We further compared the transmission ratio of forward and backward waves predicted by both methods. The transmission ratio was found to be overestimated by 10% by the classical linear method. The nonlinear method gave more accurate estimates, consistent with theory. We conclude that, for in vivo applications, the classical linear method should be the method of choice because it is simpler to use and the erros involved (4-8%) are comparable to measurement erros.
在本文中，我们研究了由于面积 - 压力关系以及对流加速度导致的流体摩擦和非线性对动脉血压和血流波分离为向前和向后分量的重要性。实验在直管状均匀非线性弹性管中进行。已经测试了涵盖生理范围的不同程度的流体摩擦和非线性。我们使用两种波分离方法预测向前和向后传播的压力分量：经典线性方法（Westerhof等人，《心血管研究》，6,648 - 656，1972）和考虑了非线性和流体摩擦的一阶校正（FOC）方法（Pythoud等人，《美国机械工程师学会生物医学工程杂志》，即将发表）。我们发现这两种方法给出的预测略有不同。差异往往随着流体摩擦和非线性程度的增加而增大，通常约为4 - 8%。我们进一步比较了两种方法预测的向前和向后波的传输比。发现经典线性方法高估了传输比10%。非线性方法给出了更准确的估计，与理论一致。我们得出结论，对于体内应用，经典线性方法应是首选方法，因为它使用更简单，且所涉及的误差（4 - 8%）与测量误差相当。
