Kenner T
Physiologisches Institut der Universität Graz, Austria.
Basic Res Cardiol. 1989 Mar-Apr;84(2):111-24. doi: 10.1007/BF01907921.
Density is defined as mass per unit volume. The classical technique to measure the density of fluids consists of a determination of mass and volume. Blood density is proportional to hematocrit or, more exactly, to the total protein concentration of blood; only to a minor extent is blood density influenced by other plasma solutes. Since the introduction of the mechanical oscillator technique for the continuous recording of fluid density a sizeable amount of experience has accumulated. This review summarizes recent work performed with this technique. It appears that the scientific interest in a variable like blood density depends on the availability of a suitable and simple method. Until the oscillator technique was available the measurement of density was too complicated or too inaccurate for routine laboratory use. A further new technique permits us to determine fluid densities by measuring sound velocity transmission. The density dilution method can be used for the determination of distribution volumes, of flow through organs, and of the cardiac output. The influence of temperature and of certain artifacts like acceleration forces in the density measuring device have to be considered any may be used for additional diagnostic purposes like determination of erythrocyte sedimentation velocity. The new technique opens a reasonable simple way to study fluid shift between interstitial space and capillaries. The arterio-venous density gradient in an organ depends on the lymph production. The injection of a hypertonic solution leads to an osmotic fluid shift from the extravascular space towards the blood. This fluid shift can be recognized by a reduction of the blood density. A simple model for the description of this reaction is presented.
密度的定义是单位体积的质量。测量流体密度的经典技术包括测定质量和体积。血液密度与血细胞比容成正比，或者更准确地说，与血液中的总蛋白浓度成正比；血液密度仅在很小程度上受其他血浆溶质的影响。自从引入用于连续记录流体密度的机械振荡器技术以来，已经积累了大量经验。本综述总结了使用该技术进行的近期工作。似乎对诸如血液密度之类变量的科学兴趣取决于是否有合适且简单的方法。在振荡器技术出现之前，密度测量对于常规实验室使用来说过于复杂或不准确。另一种新技术使我们能够通过测量声速传播来测定流体密度。密度稀释法可用于测定分布容积、器官血流量和心输出量。必须考虑温度以及密度测量设备中诸如加速力等某些伪影的影响，并且这些影响可用于诸如测定红细胞沉降速度等额外的诊断目的。这项新技术为研究组织间隙和毛细血管之间的液体转移开辟了一种相当简单的方法。器官中的动静脉密度梯度取决于淋巴生成。注射高渗溶液会导致渗透液从血管外间隙向血液转移。这种液体转移可通过血液密度的降低来识别。本文提出了一个描述该反应的简单模型。
