Department of Engineering Science, Institute of Biomedical Engineering, University of Oxford, Parks Road, Oxford OX1 3PJ, UK.
J Theor Biol. 2010 May 21;264(2):553-9. doi: 10.1016/j.jtbi.2010.03.002. Epub 2010 Mar 4.
The process known as vasomotion, rhythmic oscillations in vessel diameter, has been proposed to act as a protective mechanism for tissue under conditions of reduced perfusion, since it is frequently only observed experimentally when perfusion levels are reduced. This could be due to a resultant increase in oxygen transport from the vasculature to the surrounding tissue, either directly or indirectly. It is thus potentially of significant clinical interest as a warning signal for ischemia. However, there has been little analysis performed to quantify the effects of vessel wall movement on time-averaged mass transport. We thus present a detailed analysis of such mass transport for an axisymmetric vessel with a periodically oscillating wall, by solving the non-linear mass transport equation, and quantify the differences between the time-averaged mass transport under conditions of no oscillation (i.e. the steady-state) and varying wall oscillation amplitude. The results show that if the vessel wall alone is oscillated, with an invariant wall concentration, the time-averaged mass transport is reduced relative to the steady-state, but if the vessel wall concentration is also oscillated, then mass transport is increased, although this is generally only true when these oscillate in phase with each other. The influence of Péclet number and the non-dimensional rate of consumption of oxygen in tissue, as well as the amplitude of oscillations, are fully characterised. We conclude by considering the likely implications of these results in the context of oxygen transport to tissue.
已知血管直径的周期性波动过程即血管舒缩，被认为是在灌注减少的情况下保护组织的一种机制，因为它通常仅在灌注水平降低时才在实验中观察到。这可能是由于从脉管系统向周围组织直接或间接输送的氧气增加所致。因此，它作为缺血的预警信号具有重要的临床意义。然而，很少有分析用于量化血管壁运动对时均传质的影响。因此，我们通过求解非线性传质方程，对具有周期性壁运动的轴对称血管进行了详细的时均传质分析，并量化了无振荡（即稳态）和壁振荡幅度变化条件下的时均传质之间的差异。结果表明，如果仅使血管壁振荡，且壁浓度不变，则与稳态相比，时均传质会降低，但如果同时使血管壁浓度也振荡，则传质会增加，尽管通常只有当它们彼此同步振荡时才会如此。充分描述了佩克莱数和组织中耗氧量的无量纲速率以及振荡幅度的影响。最后，我们根据这些结果在向组织输送氧气方面的可能影响进行了讨论。
