Department of Bioinformatics, Friedrich-Schiller University, Jena, Germany.
J Appl Physiol (1985). 2012 Aug;113(3):355-67. doi: 10.1152/japplphysiol.00369.2012. Epub 2012 May 17.
An interesting problem in hemorheology is to calculate that volume fraction of erythrocytes (hematocrit) that is optimal for transporting a maximum amount of oxygen. If the hematocrit is too low, too few erythrocytes are present to transport oxygen. If it is too high, the blood is very viscous and cannot flow quickly, so that oxygen supply to the tissues is again reduced. These considerations are very important, since oxygen transport is an important factor for physical performance. Here, we derive theoretical optimal values of hematocrit in vertebrates and collect, from the literature, experimentally observed values for 57 animal species. It is an interesting question whether optimal hematocrit theory allows one to calculate hematocrit values that are in agreement with the observed values in various vertebrate species. For this, we first briefly review previous approaches in that theory. Then we check which empirical or theoretically derived formulas describing the dependence of viscosity on concentration in a suspension lead to the best agreement between the theoretical and observed values. We consider both spatially homogeneous and heterogeneous distributions of erythrocytes in the blood and also possible extensions, like the influence of defective erythrocytes and cases where some substances are transported in the plasma. By discussing the results, we critically assess the power and limitations of optimal hematocrit theory. One of our goals is to provide a systematic overview of different approaches in optimal hematocrit theory.
血液流变学中的一个有趣问题是计算出红细胞（血细胞比容）的最佳体积分数，以输送最大量的氧气。如果血细胞比容太低，输送氧气的红细胞太少。如果太高，血液非常粘稠，无法快速流动，从而再次降低组织的氧气供应。这些考虑因素非常重要，因为氧气输送是身体表现的重要因素。在这里，我们推导出脊椎动物中血细胞比容的理论最佳值，并从文献中收集了 57 种动物物种的实验观察值。一个有趣的问题是，最佳血细胞比容理论是否可以计算出与各种脊椎动物物种的观察值一致的血细胞比容值。为此，我们首先简要回顾该理论中的先前方法。然后，我们检查描述悬浮液中浓度对粘度的依赖性的经验或理论推导公式，以在理论值和观察值之间取得最佳一致。我们考虑血液中红细胞的均匀和非均匀分布，以及可能的扩展，例如红细胞缺陷和某些物质在血浆中运输的情况。通过讨论结果，我们批判性地评估了最佳血细胞比容理论的优势和局限性。我们的目标之一是提供最佳血细胞比容理论中不同方法的系统概述。
