Hypercapnia increases brain viscoelasticity
Hypercapnia increases brain viscoelasticity
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DOI：
10.1177/0271678x18799241
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发表时间：
2019-12-01
影响因子：
6.3
通讯作者：
Sack, Ingolf
中科院分区：
文献类型：
--
作者：
Hetzer, Stefan;Dittmann, Florian;Sack, Ingolf
脑功能、脑代谢活动、脑血流量（CBF）和颅内压在颅内生理学的严格自动调节机制中密切相关，其中组织粘弹性的作用仍然难以捉摸。我们将多频磁共振弹性成像 (MRE) 与 CBF 测量相结合，对 14 名暴露于富含二氧化碳的呼吸空气的健康受试者进行了 5 分钟的呼吸，以通过高碳酸血症诱导脑血管舒张。刚度和粘度通过复剪切模量 |G*| 的大小和相位角进行量化在高碳酸血症之前、期间和之后分析了全脑和 25 个灰质分区的 CBF 和 phi 以及 CBF。在所有受试者中，由于高碳酸血症，全脑硬度和粘度增加了 3.3 +/- 1.9% 和 2.0 +/- 1.1%，同时 CBF 增加了 36 +/- 15%。高碳酸血症后，|G*|和 phi 降低至正常值，而 CBF 降低至基线以下 13 +/- 15%。高碳酸血症引起的粘度变化与 CBF 变化相关，而硬度变化则不然。 MRE 测量的粘度变化与 Fahr AE us-Lindqvist 模型预测的血液粘度变化以及文献中的微血管直径变化相关。我们的结果表明，大脑粘弹性特性受到微血管血流和血液粘度的影响：高碳酸血症导致血管舒张和血液粘度增加，导致与粘度相关的 MRE 值增加。
Brain function, the brain's metabolic activity, cerebral blood flow (CBF), and intracranial pressure are intimately linked within the tightly autoregulated regime of intracranial physiology in which the role of tissue viscoelasticity remains elusive. We applied multifrequency magnetic resonance elastography (MRE) paired with CBF measurements in 14 healthy subjects exposed to 5-min carbon dioxide-enriched breathing air to induce cerebral vasodilatation by hypercapnia. Stiffness and viscosity as quantified by the magnitude and phase angle of the complex shear modulus, |G*| and phi, as well as CBF of the whole brain and 25 gray matter sub-regions were analyzed prior to, during, and after hypercapnia. In all subjects, whole-brain stiffness and viscosity increased due to hypercapnia by 3.3 +/- 1.9% and 2.0 +/- 1.1% which was accompanied by a CBF increase of 36 +/- 15%. Post-hypercapnia, |G*| and phi reduced to normal values while CBF decreased by 13 +/- 15% below baseline. Hypercapnia-induced viscosity changes correlated with CBF changes, whereas stiffness changes did not. The MRE-measured viscosity changes correlated with blood viscosity changes predicted by the Fahr AE us-Lindqvist model and microvessel diameter changes from the literature. Our results suggest that brain viscoelastic properties are influenced by microvessel blood flow and blood viscosity: vasodilatation and increased blood viscosity due to hypercapnia result in an increase in MRE values related to viscosity.