人体姿态对髂静脉压迫综合征血流特性影响

Effects of Human Postures on Flow Characteristics in Iliac Vein Compression Syndrome

目的探究不同人体姿态对髂静脉压迫综合征血流特性的影响。方法以1例含侧支代偿的盆腔型髂静脉压迫综合征患者的计算机断层影像重构髂静脉几何模型;基于计算流体动力学方法,采用非牛顿模型和多孔介质模型描述静脉嵴对血流场的影响,获取髂静脉壁面压力分布和切应力分布;运用离散相模型,探究3种人体姿态下红细胞在左髂静脉的滞留情况。结果平卧状态下压迫区域两端的压力梯度最低,而坐姿和行走状态下髂静脉呈现高压状态。3种姿态下局部最大壁面切应力均出现在侧支血管狭窄处和右髂静脉血流交汇区,其中坐姿状态下切应力最小,平卧状态下最大。坐姿状态下左髂静脉血液的滞留时间最长,为52.2 s;平卧状态下最短,为14.8 s;行走状态为23.8 s。结论采用多孔介质模型模拟静脉嵴的影响与血管造影图像高度吻合。坐姿和行走状态下的下肢静脉高压现象与临床结果一致,平卧状态能够缓解高压状况。从髂静脉的壁面切应力和血液滞留时间来看,人体在3种姿态之间不断转换,造成血管内皮损伤和血流瘀滞交替出现,增加血栓的形成风险。

Objective To investigate effects of human postures on flow characteristics of iliac vein compression syndrome.Methods The numerical model of iliac vein was reconstructed from CT images of a typical patient with pelvic-type iliac vein compression syndrome with collateral veins.Based on the computational fluid dynamics method,the non-Newtonian model and the porous media model were adopted to describe effects of abnormal structures on blood flow and acquire the wall shear stress and pressure of iliac vein.The discrete phase model was used to study the residence conditions of erythrocytes under three human postures.Results The pressure gradient at two ends of the compressive region was lowest under lying state,while the iliac vein showed a high pressure under sitting and walking states.The local maximum wall shear stresses under three postures were found at narrow segment of the collateral vein and convergence region of two flows of right iliac vein.The maximum shear stress was the largest under lying state and the smallest under sitting state.The blood residence time of 52.2 s in the left iliac vein was the longest under sitting state.The residence time of 14.8 s was shortest under lying state.The blood residence time was 23.8 s under walking state.Conclusions Porous media model used to simulate the effect of abnormal structures was highly consistent with the angiography data.The venous hypertension under sitting and walking states was consistent with the clinical result,and the lying state could relieve the hypertensive condition.In terms of wall shear stress and blood residence time in iliac vein,the continual changes between three human postures would cause endothelial damage and blood flow stasis alternately,thus increase the risk of thrombosis.