Baan J, Szidon J P, Noordergraaf A
Biophys J. 1974 May;14(5):343-62. doi: 10.1016/S0006-3495(74)85921-7.
The dynamic local distensibility of the abdominal aorta was measured in 11 anesthetized dogs by recording simultaneously phasic pressure and instantaneous intravascular cross-sectional area, utilizing a special transducer. Axial motion of the vessel wall was recorded using a modification of the same transducer. A nonlinear relationship was found to exist between area and pressure in most cases studied. Fourier analysis was performed on data from eight experiments in order to obtain frequency characteristics of distensibility. In roughly half of the cases, Fourier analysis revealed that pressure variations displayed a phase lead over area variations for frequencies up to 10 Hz. This phenomenon was ascribed to viscoelastic properties of the vessel wall and the magnitude of the phase leads roughly matched those found in vitro by others. The behavior of the vessel wall in these instances was correctly predicted by the dynamic formula for distensibility, derived by others from wave transmission theory in which absence of axial wall motion is assumed. In these experiments, axial motion of the wall was found to be virtually absent. In the other half of the cases, the reverse situation was obtained: a phase lead of area variations over pressure variations for frequencies up to 15 Hz. In those cases a craniocaudal axial displacement of the vessel wall was observed with each systole, amounting to around 1 mm. The finding of the phase leads was partially explained by a dynamic formula for distensibility, developed by us from the theory of wave transmission in which free axial motion of the wall is a chosen boundary condition. The sign and order of magnitude of the phase leads were correctly predicted by the theoretical formula, but there was a disagreement on the frequency range in which they occurred. We concluded that additional forces, not yet considered in theoretical treatments, are operative on the aortic wall, which account for this lack of agreement. The frequency dependent properties of distensibility in vivo cannot be compared to those obtained in vitro in those cases in which there is axial displacement of the vessel wall of the same order of magnitude as the radial extensions.
通过使用一种特殊的换能器同时记录相位压力和瞬时血管内横截面积，在11只麻醉犬身上测量了腹主动脉的动态局部扩张性。使用同一换能器的改进版本记录血管壁的轴向运动。在大多数研究案例中，发现面积与压力之间存在非线性关系。对来自8个实验的数据进行了傅里叶分析，以获得扩张性的频率特性。在大约一半的案例中，傅里叶分析表明，在高达10Hz的频率下，压力变化在相位上领先于面积变化。这种现象归因于血管壁的粘弹性特性，相位领先的幅度大致与其他人在体外发现的幅度相匹配。在这些情况下，血管壁的行为由其他人从假设无轴向壁运动的波传播理论推导得出的扩张性动态公式正确预测。在这些实验中，发现壁的轴向运动实际上不存在。在另一半案例中，得到了相反的情况：在高达15Hz的频率下，面积变化在相位上领先于压力变化。在那些案例中，观察到每次心脏收缩时血管壁有头尾轴向位移，总计约1mm。相位领先的发现部分由我们从波传播理论推导得出的扩张性动态公式解释，其中壁的自由轴向运动是一个选定的边界条件。理论公式正确预测了相位领先的符号和量级，但在它们出现的频率范围上存在分歧。我们得出结论，理论处理中尚未考虑的额外力作用于主动脉壁，这导致了这种不一致。在血管壁轴向位移与径向延伸具有相同量级的情况下，体内扩张性的频率依赖性特性无法与体外获得的特性进行比较。
