Convection Effect of Plasma Flow on Oxygen Transport in Capillaries: An In-Depth Numerical Investigation

IF 1.9 4区医学 Q3 HEMATOLOGY

Microcirculation Pub Date : 2025-04-20 DOI:10.1111/micc.70011

Junfeng Zhang

{"title":"Convection Effect of Plasma Flow on Oxygen Transport in Capillaries: An In-Depth Numerical Investigation","authors":"Junfeng Zhang","doi":"10.1111/micc.70011","DOIUrl":null,"url":null,"abstract":"<div>\n \n \n <section>\n \n <h3> Objective</h3>\n \n <p>The convection effect of plasma flow on gas transport in the microcirculation has been a controversial topic in the literature. We aim to clarify this concern via thorough and rigorous analysis of the oxygen release process from red blood cells (RBCs) to the surrounding tissue.</p>\n </section>\n \n <section>\n \n <h3> Methods</h3>\n \n <p>We develop a comprehensive model that considers the plasma flow, RBC deformation, oxygen transport and oxygen-hemoglobin reaction kinetics. The boundary integral and lattice Boltzmann methods are employed in the numerical solutions. In particular, the oxygen fluxes due to plasma convection and mass diffusion are separately calculated along the capillary wall for further comparison.</p>\n </section>\n \n <section>\n \n <h3> Results</h3>\n \n <p>Our results show that the most significant diffusive flux occurs in the narrow gap between the RBC side surface and the capillary wall and the diffusive flux is primarily directed outward, which favors oxygen release into the surrounding tissue. Furthermore, although the axial convective flux is the most profound in magnitude, it contributes little to the overall blood-to-tissue oxygen transport in the radial direction. The radial convective flux also has a larger magnitude compared to the diffusive oxygen flux, but is limited to two small areas and to opposite directions. This results in a negligible net effect of the plasma convection compared to the diffusive flux on the overall oxygen transport. This observation is further confirmed by comparing the oxygen distributions and diffusive fluxes from simulations with and without considering the plasma convection flow relative to RBCs. Moreover, we revisit the Peclet number definition and propose that different characteristic length scales should be adopted for oxygen diffusion and convection in capillaries. The revised Peclet number has a value three orders of magnitude lower than that from the classical Peclet number definition.</p>\n </section>\n \n <section>\n \n <h3> Conclusions</h3>\n \n <p>Our simulation results show that the influence of plasma convection on the overall oxygen transport can be neglected in typical microcirculation situations. This is consistent with the revised Peclet number value, suggesting that the revised Peclet number can better reflect the relative importance of convection and diffusion mechanisms in microvascular gas transport.</p>\n </section>\n </div>","PeriodicalId":18459,"journal":{"name":"Microcirculation","volume":"32 3","pages":""},"PeriodicalIF":1.9000,"publicationDate":"2025-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/micc.70011","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Microcirculation","FirstCategoryId":"3","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/micc.70011","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"HEMATOLOGY","Score":null,"Total":0}

引用次数: 0

Abstract

Objective

The convection effect of plasma flow on gas transport in the microcirculation has been a controversial topic in the literature. We aim to clarify this concern via thorough and rigorous analysis of the oxygen release process from red blood cells (RBCs) to the surrounding tissue.

Methods

We develop a comprehensive model that considers the plasma flow, RBC deformation, oxygen transport and oxygen-hemoglobin reaction kinetics. The boundary integral and lattice Boltzmann methods are employed in the numerical solutions. In particular, the oxygen fluxes due to plasma convection and mass diffusion are separately calculated along the capillary wall for further comparison.

Results

Our results show that the most significant diffusive flux occurs in the narrow gap between the RBC side surface and the capillary wall and the diffusive flux is primarily directed outward, which favors oxygen release into the surrounding tissue. Furthermore, although the axial convective flux is the most profound in magnitude, it contributes little to the overall blood-to-tissue oxygen transport in the radial direction. The radial convective flux also has a larger magnitude compared to the diffusive oxygen flux, but is limited to two small areas and to opposite directions. This results in a negligible net effect of the plasma convection compared to the diffusive flux on the overall oxygen transport. This observation is further confirmed by comparing the oxygen distributions and diffusive fluxes from simulations with and without considering the plasma convection flow relative to RBCs. Moreover, we revisit the Peclet number definition and propose that different characteristic length scales should be adopted for oxygen diffusion and convection in capillaries. The revised Peclet number has a value three orders of magnitude lower than that from the classical Peclet number definition.

Conclusions

Our simulation results show that the influence of plasma convection on the overall oxygen transport can be neglected in typical microcirculation situations. This is consistent with the revised Peclet number value, suggesting that the revised Peclet number can better reflect the relative importance of convection and diffusion mechanisms in microvascular gas transport.

Abstract Image

查看原文本刊更多论文

等离子体流对毛细血管中氧传输的对流效应：一个深入的数值研究

目的等离子体对流对微循环中气体输运的影响一直是文献中有争议的话题。我们的目标是通过对红细胞（rbc）向周围组织的氧气释放过程进行彻底和严格的分析来澄清这一问题。方法建立一个综合考虑血浆流动、红细胞变形、氧转运和氧血红蛋白反应动力学的模型。数值解采用边界积分法和点阵玻尔兹曼方法。为了进一步比较，我们分别计算了等离子体对流和质量扩散引起的氧通量。结果红细胞侧壁与毛细血管壁之间的狭窄间隙处弥散通量最大，且弥散通量主要向外，有利于氧向周围组织释放。此外，虽然轴向对流通量的幅度最大，但它对血液到组织的整体氧在径向上的运输贡献很小。径向对流通量也比扩散氧通量具有更大的量级，但仅限于两个小区域和相反的方向。这导致等离子体对流的净效应与扩散通量对整个氧输运的净效应相比可以忽略不计。通过比较考虑和不考虑相对于红细胞的等离子体对流流的模拟的氧分布和扩散通量，进一步证实了这一观察结果。此外，我们重新审视了Peclet数的定义，并提出了氧气在毛细管中的扩散和对流应采用不同的特征长度尺度。修正后的佩莱特数的值比经典佩莱特数定义的值低三个数量级。结论模拟结果表明，在典型微循环条件下，等离子体对流对整体氧输运的影响可以忽略不计。这与修正后的Peclet数值一致，说明修正后的Peclet数能更好地反映对流和扩散机制在微血管气体输送中的相对重要性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

Microcirculation 医学-外周血管病

CiteScore

5.00

自引率

4.20%

发文量

审稿时长

6-12 weeks

期刊介绍： The journal features original contributions that are the result of investigations contributing significant new information relating to the vascular and lymphatic microcirculation addressed at the intact animal, organ, cellular, or molecular level. Papers describe applications of the methods of physiology, biophysics, bioengineering, genetics, cell biology, biochemistry, and molecular biology to problems in microcirculation. Microcirculation also publishes state-of-the-art reviews that address frontier areas or new advances in technology in the fields of microcirculatory disease and function. Specific areas of interest include: Angiogenesis, growth and remodeling; Transport and exchange of gasses and solutes; Rheology and biorheology; Endothelial cell biology and metabolism; Interactions between endothelium, smooth muscle, parenchymal cells, leukocytes and platelets; Regulation of vasomotor tone; and Microvascular structures, imaging and morphometry. Papers also describe innovations in experimental techniques and instrumentation for studying all aspects of microcirculatory structure and function.