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首页> 外文期刊>Journal of Theoretical Biology >Cerebral perfusion pressure in giraffe: modelling the effects of head-raising and -lowering.
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Cerebral perfusion pressure in giraffe: modelling the effects of head-raising and -lowering.

机译：长颈鹿的脑灌注压：模拟抬头和放低头的效果。

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Loss of consciousness caused by positional changes of the head results from reduced cerebral blood flow (CBF). CBF is related to cerebral perfusion pressure (CPP). CPP is the difference between mean arterial pressure (MAP) at the head and intracranial pressure (ICP). The positional change of the giraffe head between ground level and standing upright is the largest of all animals yet loss of consciousness does not occur. We have investigated the possibility that an increase in CPP protects giraffe from fainting, using a mechanical model that functioned as an anatomical U-tube. It consisted of a rigid ascending "carotid" limb, a collapsible "brain" tube drained by a rigid, "vertebral venous plexus" (VVP) tube, and a collapsible "head" tube drained by a collapsible tube representing the "jugular vein". The descending tubes could be rotated relative to the "carotid" tube to be horizontal, or at 30 degrees , 45 degrees , and 60 degrees to the vertical to simulate changes in head position. Pressure at the top of the "carotid" tube was intracranial MAP, at the top of the "VVP" tube was ICP, and the difference CPP. In the simulated "head-up" position and a fluid flow rate of 4 L min(-1), CPP was approximately 170 mmHg. With the VVP tube horizontal, CPP fell from approximately 170 to 45 mmHg, but increased to approximately 67 mmHg at 30 degrees "down", to approximately 70 mmHg at 45 degrees "down" and to approximately 75 at 60 degrees "down". The fall in CPP in the head-down positions resulted from a decrease in viscous resistance in, and dissipation of pressure to, the "head" and "jugular" tubes. These data provide an estimate of cranial pressure changes in giraffe during positional changes of the head, and suggest that an increase in CPP plays a significant role in maintaining CBF during head-raising and that it may be an important mechanism for preventing fainting in giraffe.
机译：头部位置改变引起的意识丧失是由于脑血流量减少（CBF）引起的。 CBF与脑灌注压（CPP）有关。 CPP是头部平均动脉压（MAP）与颅内压（ICP）之差。在所有动物中，长颈鹿头在地面和直立之间的位置变化是最大的，但不会发生意识障碍。我们已经研究了CPP升高保护长颈鹿免于晕倒的可能性，方法是使用机械模型作为解剖U形管。它由一个刚性上升的“颈动脉”肢，一个由刚性“椎静脉丛”（VVP）引流的可折叠“脑”管和一个由代表“颈静脉”的可折叠管引流的可折叠“头”管组成。 。下降管可以相对于“颈动脉”管旋转为水平，或相对于垂直轴旋转30度，45度和60度，以模拟头部位置的变化。 “颈动脉”管顶部的压力为颅内MAP，“ VVP”管顶部的压力为ICP，差CPP。在模拟的“抬头”位置和4 L min（-1）的流体流速下，CPP约为170 mmHg。在VVP管水平的情况下，CPP从大约170毫米汞柱下降到45毫米汞柱，但在“向下” 30度上升到大约67毫米汞柱，在“向下” 45度上升到大约70毫米汞柱，在“向下” 45度上升到大约75毫米汞柱。头朝下位置的CPP下降是由于“头”和“颈”管中的粘性阻力降低以及压力消散的缘故。这些数据提供了在头部位置变化过程中长颈鹿的颅压变化的估计值，并表明CPP的升高在抬头过程中维持CBF方面起着重要作用，并且它可能是防止长颈鹿晕厥的重要机制。

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