Biomechanics of Retinal Venous Pulsations as Indicators of Intracranial Pressure
Biomechanics of Retinal Venous Pulsations as Indicators of Intracranial Pressure
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作为颅内压指标的视网膜静脉搏动的生物力学
DOI：
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发表时间：
2016
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通讯作者：
C. Babbs
中科院分区：
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作者：
C. Babbs
视网膜静脉搏动的起源在生理学和医学上仍然是一个悬而未决的问题，它们与颅内压的确切关系也是如此。本研究采用数学建模的方法来探索通过眼睛的血流细节，以揭示脉动的机制。视网膜动脉和静脉的阴道内、神经内和眼内段被建模为连接的电容性-电容性段。该分析结合了这些小血管的两个关键的机械性能，迄今为止没有研究过，这在负透壁压的条件下变得重要：（1）在变平期间显著降低的顺应性和（2）随着内部体积减小，横截面形状变化。作用于这些靠近视盘的静脉上的眼内压通常会产生波动的负透壁压。观察到的这些静脉段的长直径在舒张期变宽，因为它们排空和变平，并且在收缩期变窄，因为它们重新充满血液。这种可见的脉动只发生在包括非线性顺应性和恒定周长平坦的模型中。此外，当颅内压升高、海绵窦压升高或小动脉阻力降低使所有视网膜静脉中的内压升高到眼内压水平以上时，搏动消失。在这种情况下，透壁静脉压总是正的，横截面形状是圆形的，并且顺应性大大降低。然后可见的视网膜静脉搏动消失。建议的情况下，颅内压可以定量估计视网膜静脉搏动的体检，如果眼内压也测量。
The origin of retinal venous pulsations remains an open problem in physiology and medicine; so too, their exact relationship to intracranial pressure. This study takes a mathematical modeling approach to explore details of blood flow through the eye to reveal the mechanism of pulsations. The intravaginal, intraneural, and intraocular segments of the retinal arteries and veins are modeled as connected resistive-capacitive segments. The analysis incorporates two critical mechanical properties of these small blood vessels, not heretofore studied, which become significant under conditions of negative transmural pressures: (1) dramatically reduced compliance during flattening and (2) cross-sectional shape change as internal volume decreases. Intraocular pressure acting on these veins close to the optic disc normally creates fluctuating negative transmural pressure. The observed long diameters of these venous segments become wider during diastole as they empty and flatten and narrower during systole as they refill with blood. Such visible pulsations occur only in models that include nonlinear compliance and constant-perimeter flattening. Further, the pulsations disappear when raised intracranial pressure, raised cavernous sinus pressure, or reduced arteriolar resistance elevates internal pressure in all retinal veins above the level of intraocular pressure. In this case transmural venous pressures are always positive, cross sectional shapes are circular, and compliance is greatly reduced. Then visible retinal venous pulsations disappear. Scenarios are suggested under which intracranial pressure can be estimated quantitatively from physical examination of retinal venous pulsations, if intraocular pressure is also measured.