Myers L J, Capper W L
Department of Human Biology, Faculty of Health Science, University of Cape Town, Observatory 7925, Cape Town, South Africa.
Med Eng Phys. 2002 May;24(4):285-94. doi: 10.1016/s1350-4533(02)00019-x.
A transmission line model of the human foetal circulatory system is presented. The model has been developed in the frequency domain with the cardiac input modeled as a flow rather than as a pressure pulse and is structured upon electrical transmission line analogies. The model is formed by cascading solutions to the two-dimensional Navier-Stokes equations for both oscillatory and steady, laminar viscous fluid flow in isotropic visco-elastic tubes with thick walls, which are constrained by surrounding tissues. Simulations allow for representation of both forward and retrograde travelling flow and pressure waves in all of the main foetal arterial vessels. The solution is verified by a comparison of model generated Doppler indices in the thoracic aorta, abdominal aorta, iliac artery and both ends of the umbilical arteries with previously published indices obtained by clinical measurements in these arteries. For simulations of blood flow in a healthy foetus, the model generated Pulsatility and Resistance indices were on average within 8% of the corresponding clinical measurements. The model results also demonstrates that placental resistance must increase by a factor of three, corresponding to a 60% decrease in flow to the placenta, before umbilical arterial absent end diastolic flow is observed. Differences between indices obtained from simulations at opposite ends of the umbilical arteries increase with increasing placental resistance.
本文提出了一种人类胎儿循环系统的传输线模型。该模型是在频域中开发的，将心脏输入建模为流量而非压力脉冲，并基于电传输线类比构建。该模型由对二维Navier-Stokes方程的级联解构成，用于模拟在具有厚壁的各向同性粘弹性管中，受周围组织约束的振荡和稳定层流粘性流体流动。模拟能够呈现所有主要胎儿动脉血管中的正向和逆向行波血流及压力波。通过将模型生成的胸主动脉、腹主动脉、髂动脉和脐动脉两端的多普勒指数与先前发表的通过这些动脉临床测量获得的指数进行比较，验证了解决方案。对于健康胎儿的血流模拟，模型生成的搏动性和阻力指数平均在相应临床测量值的8%以内。模型结果还表明，在观察到脐动脉舒张期末端血流消失之前，胎盘阻力必须增加三倍，相当于流向胎盘的血流量减少60%。脐动脉两端模拟获得的指数差异随胎盘阻力增加而增大。
