Cardiovascular Aging Research Laboratory, Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, TX, USA.
Vasc Med. 2012 Aug;17(4):231-4. doi: 10.1177/1358863X12450095.
Flow-mediated dilation (FMD) is a non-invasive index of endothelial function. In an attempt to standardize FMD for shear stimulus, shear rate (velocity/diameter), rather than shear stress (viscosity*velocity/diameter), is commonly used as a surrogate measure, although it is limited by individual differences in blood viscosity. The purpose of this study was to determine the contribution of whole blood viscosity to FMD and other key measures of vascular function. Blood viscosity, FMD, carotid artery compliance, and carotid-femoral pulse wave velocity (cfPWV) were measured in 98 apparently healthy adults varying widely in age (18-63 years). Whole blood viscosity was not significantly correlated with FMD, cfPWV, or carotid artery compliance. Shear rate was a stronger correlate with FMD than shear stress that takes blood viscosity into account (r = 0.43 vs 0.28). No significant differences were observed between whole blood viscosity and traditional risk factors for cardiovascular disease. Age was positively correlated with cfPWV (r = 0.65, p < 0.001) and negatively correlated with FMD (r = -0.24, p < 0.05) and carotid artery compliance (r = -0.45, p < 0.01). Controlling for viscosity did not reduce the strength of these relations. These results indicate that whole blood viscosity does not significantly impact measures of vascular function and suggests that the common practice to use shear rate, rather than shear stress, in the adjustment of FMD is valid.
血流介导的扩张（FMD）是内皮功能的一种非侵入性指标。为了使切变刺激标准化，通常使用切变率（速度/直径）而不是切变应力（粘度*速度/直径）作为替代测量值，尽管它受到个体血液粘度差异的限制。本研究旨在确定全血粘度对 FMD 和其他血管功能关键指标的贡献。在 98 名年龄范围广泛（18-63 岁）的健康成年人中测量了全血粘度、FMD、颈动脉顺应性和颈动脉-股动脉脉搏波速度（cfPWV）。全血粘度与 FMD、cfPWV 或颈动脉顺应性均无显著相关性。切变率与 FMD 的相关性强于考虑血液粘度的切变应力（r = 0.43 与 0.28）。全血粘度与心血管疾病传统危险因素之间未观察到显著差异。年龄与 cfPWV 呈正相关（r = 0.65，p < 0.001），与 FMD（r = -0.24，p < 0.05）和颈动脉顺应性（r = -0.45，p < 0.01）呈负相关。控制粘度并没有降低这些关系的强度。这些结果表明全血粘度对血管功能测量值没有显著影响，并表明在调整 FMD 时使用切变率而不是切变应力的常见做法是有效的。
