Differential blood flow responses to CO2 in human internal and external carotid and vertebral arteries
Differential blood flow responses to CO2 in human internal and external carotid and vertebral arteries
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DOI：
10.1113/jphysiol.2012.230425
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发表时间：
2012-07-01
影响因子：
5.5
通讯作者：
Ogoh, Shigehiko
中科院分区：
文献类型：
--
作者：
Sato, Kohei;Sadamoto, Tomoko;Ogoh, Shigehiko
关键点动脉二氧化碳是脑血流量的中介物，其对脑血流调节的相对影响被定义为脑二氧化碳反应性。由于方法学的限制，以前几乎所有的研究都评估了大脑中动脉血流速度对二氧化碳变化的反应，作为衡量整个大脑中二氧化碳反应的指标。我们发现椎动脉的二氧化碳反应性比颈内动脉低。此外，颈外动脉的二氧化碳反应性明显低于脑循环。这些结果表明，在颈内、颈外和椎基底动脉循环中，二氧化碳对血流的调节存在区域性差异。摘要动脉二氧化碳是脑血流量的中介物，其对脑血流量调节的相对影响被定义为脑二氧化碳反应性。我们以前的研究已经证明，人类不同的动脉对生理刺激(即动态运动和立位应激)的CBF反应存在差异。这些结果提示，脑前循环和脑后循环的动态CBF调节和脑CO2反应性可能不同。这项研究的目的是通过测量血流量来确定大脑的二氧化碳反应性，并检查颈内动脉(ICA)、颈外动脉(ECA)和椎动脉(VA)之间二氧化碳反应性的潜在差异。在10名健康青年受试者中，我们用双功超声(Vivid-e，GE Healthcare)和经颅多普勒(Vivid-7，GE Healthcare)检测了高二氧化碳(3%和6%二氧化碳)、正常二氧化碳和低二氧化碳时大脑中动脉(MCA)和基底动脉(BA)的平均血流速度，以评估二氧化碳的反应性。为了表征脑血管对二氧化碳的反应性，我们在CBF和估计的动脉二氧化碳分压之间进行了指数和线性回归分析，通过呼气末二氧化碳分压计算得出。VA的二氧化碳反应性显著低于ICA(指数回归系数0.021+/-0.008比0.030+/-0.008；线性回归斜率2.11+/-0.84比3.18+/-1.09%毫米汞-1：VA比ICA，P<；0.01)。大脑后循环中的低二氧化碳反应性在远端颅内动脉持续存在(指数0.023+/-0.006比0.037+/-0.009；线性2.29+/-0.56比3.31+/-0.87%毫米汞-1：BA比大脑中动脉)。相反，二氧化碳在ECA中的反应性明显低于脑内循环(指数0.006+/-0.007；线性0.63+/-0.64%毫米汞-1，P<；0.01)。这些结果表明，椎基底动脉循环的CO2反应性低于颈内循环，颈外循环的CO2反应性明显低于脑循环，这可能是CBF对生理应激反应不同的原因。
Key points Arterial CO2 serves as a mediator of cerebral blood flow, and its relative influence on the regulation of cerebral blood flow is defined as cerebral CO2 reactivity. Because of methodological limitations, almost all previous studies have evaluated the response of blood flow velocity in the middle cerebral artery to changes in CO2 as a measure of CO2 reactivity across the whole brain. We found that the vertebral artery has lower CO2 reactivity than the internal carotid artery. Moreover, CO2 reactivity in the external carotid artery was markedly lower than in the cerebral circulation. These results demonstrate regional differences in CO2 regulation of blood flow between the internal carotid, external carotid, and vertebro-basilar circulation. Abstract Arterial CO2 serves as a mediator of cerebral blood flow (CBF), and its relative influence on the regulation of CBF is defined as cerebral CO2 reactivity. Our previous studies have demonstrated that there are differences in CBF responses to physiological stimuli (i.e. dynamic exercise and orthostatic stress) between arteries in humans. These findings suggest that dynamic CBF regulation and cerebral CO2 reactivity may be different in the anterior and posterior cerebral circulation. The aim of this study was to identify cerebral CO2 reactivity by measuring blood flow and examine potential differences in CO2 reactivity between the internal carotid artery (ICA), external carotid artery (ECA) and vertebral artery (VA). In 10 healthy young subjects, we evaluated the ICA, ECA, and VA blood flow responses by duplex ultrasonography (Vivid-e, GE Healthcare), and mean blood flow velocity in middle cerebral artery (MCA) and basilar artery (BA) by transcranial Doppler (Vivid-7, GE healthcare) during two levels of hypercapnia (3% and 6% CO2), normocapnia and hypocapnia to estimate CO2 reactivity. To characterize cerebrovascular reactivity to CO2, we used both exponential and linear regression analysis between CBF and estimated partial pressure of arterial CO2, calculated by end-tidal partial pressure of CO2. CO2 reactivity in VA was significantly lower than in ICA (coefficient of exponential regression 0.021 +/- 0.008 vs. 0.030 +/- 0.008; slope of linear regression 2.11 +/- 0.84 vs. 3.18 +/- 1.09% mmHg-1: VA vs. ICA, P < 0.01). Lower CO2 reactivity in the posterior cerebral circulation was persistent in distal intracranial arteries (exponent 0.023 +/- 0.006 vs. 0.037 +/- 0.009; linear 2.29 +/- 0.56 vs. 3.31 +/- 0.87% mmHg-1: BA vs. MCA). In contrast, CO2 reactivity in ECA was markedly lower than in the intra-cerebral circulation (exponent 0.006 +/- 0.007; linear 0.63 +/- 0.64% mmHg-1, P < 0.01). These findings indicate that vertebro-basilar circulation has lower CO2 reactivity than internal carotid circulation, and that CO2 reactivity of the external carotid circulation is markedly diminished compared to that of the cerebral circulation, which may explain different CBF responses to physiological stress.