Kocsis Laszlo, Herman Peter, Eke Andras
Institute of Human Physiology and Clinical Experimental Research, Semmelweis University, Faculty of Medicine, P.O. Box 448, Budapest 1446, Hungary.
J Theor Biol. 2006 Jul 21;241(2):262-75. doi: 10.1016/j.jtbi.2005.11.033. Epub 2006 Jan 18.
This article presents a quasistatic, compartmental model of tissue-level hemodynamics and oxygenation that leads to a set of formulas, which is suitable to calculate important physiological variables from the mean tissue concentration and saturation of hemoglobin, measured by tissue spectroscopy. Dimensioned quantities are represented relative to their baseline value in the equations (relative value = perturbed/baseline). All model parameters are non-dimensional. The model is based and extends on a number of previous works: previous models of similar aim and scope are consolidated, and every critical assumptions and approximations are treated explicitly; extensions include for example the incorporation of the Fahraeus-effect and the separate estimation of the volume changes of the arterial and the venous compartments. The information content of spectroscopic data alone is shown to be valuable, but limited: the relative venous volume, the oxygen extraction fraction and the relative cellulovascular coupling (defined as the ratio of blood flow and oxygen consumption) can be calculated from these data, if the alterations in arterial blood volume are negligible. The number of variables estimated by the derived formulas can be increased if local blood flow is measured simultaneously: in this case, the relative arterial and venous volume and resistance, the oxygen extraction fraction, and the relative oxygen consumption can be determined. Given that this model considers arterial blood pressure, saturation and hematocrit as its inputs, when measured, the model becomes applicable in such conditions as hyper- or hypotension, hypoxic hypoxia, hemodilution and hemorrhage, where these variables do change. The estimation of the changes in arterial resistance can be applied to estimate the extent of an autoregulatory response.
本文提出了一种组织水平血液动力学和氧合的准静态、分区模型，该模型导出了一组公式，适用于根据组织光谱测量的血红蛋白平均组织浓度和饱和度来计算重要的生理变量。在方程中，有量纲的量相对于其基线值表示（相对值 = 扰动值/基线值）。所有模型参数都是无量纲的。该模型基于并扩展了许多先前的工作：整合了具有类似目标和范围的先前模型，并明确处理了每个关键假设和近似值；扩展内容例如包括纳入法赫瑞厄斯效应以及分别估计动脉和静脉腔室的体积变化。结果表明，仅光谱数据的信息内容是有价值的，但也是有限的：如果动脉血容量的变化可忽略不计，则可以从这些数据中计算相对静脉体积、氧摄取分数和相对细胞血管耦合（定义为血流量与氧消耗的比值）。如果同时测量局部血流量，则通过推导公式估计的变量数量可以增加：在这种情况下，可以确定相对动脉和静脉体积及阻力、氧摄取分数和相对氧消耗。鉴于该模型将动脉血压、饱和度和血细胞比容作为输入，在进行测量时，该模型适用于动脉血压过高或过低、低氧性缺氧、血液稀释和出血等这些变量确实发生变化的情况。动脉阻力变化的估计可用于评估自动调节反应的程度。
