Chang K C, Kuo T S
Department of Physiology, College of Medicine, National Taiwan University, Taipei.
J Theor Biol. 1996 Nov 7;183(1):35-46. doi: 10.1006/jtbi.1996.0199.
There is no question that geometric and elastic tapering is the rule of the nature of the mammalian arterial system. In this investigation, we determine the role of an exponentially tapered T-tube model to characterize the non-uniform nature and physical properties of the vasculature. The tapering feature could be inferred to show a connection between characteristic impedance at the distal of the tube and that at the entrance of the tube. Pulsatile pressure and flow signals of the ascending aorta were measured in 12 closed-chest, anesthetized dogs. This non-uniform T-tube model fits the measured aortic pressure waveform well. The mathematical and experimental model impedance spectra are similar. In the basal state, the distal characteristic impedance is 9.5% higher than the input characteristic impedance. The input characteristic impedance estimated in the model is compatible with that calculated by averaging high-frequency moduli of impedance data points obtained from the ratio of the corresponding harmonics of pressure and flow. Furthermore, the exponentially tapered T-tube model has a close estimate in wave transit time when compared with that computed by the impulse response of the filtered aortic input impedance. These data suggest that inclusion of tube tapering improves the mathematical model so that it is capable of characterizing the non-uniform nature of the arterial system. We conclude that the non-uniform properties of wave-transmission paths play an important role in governing the behavior of an asymmetric T-tube for the representation of the arterial system.
毫无疑问，几何形状和弹性逐渐变细是哺乳动物动脉系统的自然规律。在本研究中，我们确定指数渐变T形管模型在表征血管系统的非均匀性质和物理特性方面的作用。可以推断，渐变特征表明管远端的特征阻抗与管入口处的特征阻抗之间存在联系。在12只开胸麻醉犬中测量了升主动脉的脉动压力和流量信号。这种非均匀T形管模型与测得的主动脉压力波形拟合良好。数学模型和实验模型的阻抗谱相似。在基础状态下，远端特征阻抗比输入特征阻抗高9.5%。模型中估计的输入特征阻抗与通过对从压力和流量的相应谐波之比获得的阻抗数据点的高频模量进行平均计算得到的结果相符。此外，与通过滤波后的主动脉输入阻抗的脉冲响应计算得到的波传播时间相比，指数渐变T形管模型的估计值与之相近。这些数据表明，考虑管的渐变可以改进数学模型，使其能够表征动脉系统的非均匀性质。我们得出结论，波传播路径的非均匀特性在控制用于表示动脉系统的不对称T形管的行为方面起着重要作用。
