Nocke H, Meyer F, Lessmann V
Institut für Physiologie, Universitätsklinikum Magdeburg A. ö. R., Magdeburg, Deutschland.
Klinik für Allgemein-, Viszeral- & Gefäßchirurgie, Universitätsklinikum Magdeburg A. ö. R., Magdeburg, Deutschland.
Zentralbl Chir. 2014 Oct;139(5):499-507. doi: 10.1055/s-0032-1327967. Epub 2013 Jan 16.
To be able to evaluate properly a vascular problem, basic concepts of vascular physiology need to be considered, as they have been taught in physiology for a long time. This article deals with selected definitions and laws of passive vascular mechanics, subdivided into parameters of vascular filling and parameters of vascular flow. PARAMETERS OF VASCULAR FILLING: During vascular filling the transmural pressure distends the vascular wall until it is balanced by the wall tension. The extent of this distension up to the point of balance depends on the elasticity of the wall. Transmural pressure, wall tension and elasticity are defined, and their respective importance is described by clinical examples, e.g. aneurysm and varix. PARAMETERS OF VASCULAR FLOW: The vascular flow can be divided into stationary and pulsating components. Both components are relevant for the bloodstream. Since the blood flow is directed in the circuit, it can be understood in first approximation as stationary ("direct current").The direct current model uses only the average values of the pulsating variables. The great advantage of the direct current model is that it can be described with simple laws, which are not valid without reservation, but often allow a first theoretical approach to a vascular problem: Ohm's law, driving pressure, flow resistance, Hagen-Poiseuille law, wall shear stress, law of continuity, Bernoulli's equation and Reynold's number are described and associated with clinical examples.The heart is a pressure-suction pump and produces a pulsating flow, the pulse. The pulse runs with pulse wave velocity, which is much larger than the blood flow velocity, through the arterial vascular system. During propagation, the pulse has to overcome the wave resistance (impedance). Wherever the wave resistance changes, e.g., at vascular bifurcations and in the periphery, it comes to reflections. The incident (forward) and reflected (backward) waves are superimposed to yield the resulting pulse wave. This pulse wave allows one to distinguish pressure and flow pulse by measurement. Both are described separately, and their respective clinical meaning is illustrated by appropriate examples, e.g., arterial stiffness and pre-/postocclusive high/low resistance flow, respectively.
为了能够正确评估血管问题，需要考虑血管生理学的基本概念，这些概念在生理学中已经讲授了很长时间。本文讨论了被动血管力学的选定定义和定律，分为血管充盈参数和血管流动参数。血管充盈参数：在血管充盈过程中，跨壁压力使血管壁扩张，直到被壁张力平衡。这种扩张到平衡点的程度取决于壁的弹性。定义了跨壁压力、壁张力和弹性，并通过临床实例（如动脉瘤和静脉曲张）描述了它们各自的重要性。血管流动参数：血管流动可分为稳态和脉动成分。这两个成分都与血流相关。由于血流在循环中是定向的，在初步近似中可以理解为稳态（“直流电”）。直流模型仅使用脉动变量的平均值。直流模型的一大优点是可以用简单的定律来描述，这些定律并非毫无保留地有效，但通常能为血管问题提供初步的理论方法：描述了欧姆定律、驱动压力、流动阻力、哈根 - 泊肃叶定律、壁面剪应力、连续性定律、伯努利方程和雷诺数，并结合临床实例进行说明。心脏是一个压力 - 抽吸泵，产生脉动血流，即脉搏。脉搏以比血流速度大得多的脉搏波速度通过动脉血管系统。在传播过程中，脉搏必须克服波阻（阻抗）。无论波阻在哪里发生变化，例如在血管分支处和外周，都会产生反射。入射（向前）波和反射（向后）波叠加产生合成脉搏波。通过测量这种脉搏波可以区分压力脉搏和血流脉搏。分别对两者进行了描述，并通过适当的实例（如分别为动脉僵硬度和闭塞前/后高/低阻力血流）说明了它们各自的临床意义。
