Intaglietta M, Johnson P C, Winslow R M
Department of Bioengineering, University of California, San Diego, La Jolla 92093-0412, USA.
Cardiovasc Res. 1996 Oct;32(4):632-43.
Understanding of oxygen delivery by the microcirculation has been dominated by the unitary component analysis of Krogh and Erlangen focussed on oxygen transport mediated by single capillaries, oxygenation of tissue as a whole being extrapolated from findings on oxygen exchange in these vessels. This analysis is under revision since capillaries are not sole sources of oxygen. It is increasingly apparent that arterioles are a significant equivalent source, while venules may serve as sinks for capillary and arteriolar oxygen. As a consequence detailed descriptions of the architecture of the microcirculation based on the tissue cylinder conceptualization does not yield new information given the non-exclusive role of capillaries as purveyors of oxygen to tissue. In the present study we investigate how tissue is oxygenated directly from the arteriolar supply on the basis of current results with newly developed optical techniques for the measurement of local intra- and extravascular pO2 by phosphorescence decay. This methodology shows that tissue regions between arterioles and venules have essentially uniform tissue pO2. The only experimentally detectable gradients in pO2 are those present in the immediate vicinity of arterioles. Findings on vascular longitudinal gradients are used to devise a model that links convective and diffusive processes, showing how blood viscosity, blood oxygen-carrying capacity and the slope of the oxygen dissociation curve are linked in determining intravascular and tissue pO2. The integrated approach provides a numerical basis for interpreting consequences of alterations in transport properties of blood applicable to the field of blood substitutes.
对微循环氧输送的理解一直以克罗格和埃尔朗根的单一成分分析为主导，该分析聚焦于由单个毛细血管介导的氧运输，将整个组织的氧合作用从这些血管中氧交换的研究结果推断而来。由于毛细血管并非氧的唯一来源，这种分析正在被修正。越来越明显的是，小动脉是一个重要的等效氧源，而小静脉可能充当毛细血管和小动脉氧的汇。因此，基于组织圆柱体概念化对微循环结构的详细描述，鉴于毛细血管作为组织氧供应者的非排他性作用，并不会产生新的信息。在本研究中，我们基于当前利用新开发的通过磷光衰减测量局部血管内和血管外pO₂的光学技术所取得的结果，研究组织如何直接从小动脉供应中获得氧合。这种方法表明，小动脉和小静脉之间的组织区域具有基本均匀的组织pO₂。唯一在实验中可检测到的pO₂梯度是小动脉紧邻区域存在的那些。关于血管纵向梯度的研究结果被用于设计一个将对流和扩散过程联系起来的模型，展示了血液粘度、血液携氧能力和氧解离曲线的斜率在决定血管内和组织pO₂时是如何相互关联的。这种综合方法为解释血液运输特性改变的后果提供了一个数值基础，适用于血液替代品领域。
