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首页> 外文期刊>American Journal of Physiology >Standing up to the challenge of standing: a siphon does not support cerebral blood flow in humans.
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Standing up to the challenge of standing: a siphon does not support cerebral blood flow in humans.

机译：直立的挑战：虹吸不支持人类的脑部血液流动。

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Model studies have been advanced to suggest both that a siphon does and does not support cerebral blood flow in an upright position. If a siphon is established with the head raised, it would mean that internal jugular pressure reflects right atrium pressure minus the hydrostatic difference from the brain. This study measured spinal fluid pressure in the upright position, the pressure and the ultrasound-determined size of the internal jugular vein in the supine and sitting positions, and the internal jugular venous pressure during seated exercise. When the head was elevated approximately 25 cm above the level of the heart, internal jugular venous pressure decreased from 9.5 (SD 2.8) to 0.2 (SD 1.0) mmHg [n = 15; values are means (SD); P < 0.01]. Similarly, central venous pressure decreased from 6.2 (SD 1.8) to 0.6 (SD 2.6) mmHg (P < 0.05). No apparent lumen was detected in any of the 31 left or right internal veins imaged at 40 degrees head-up tilt, and submaximal (n = 7) and maximal exercise (n = 4) did not significantly affect internal jugular venous pressure. While seven subjects were sitting up, spinal fluid pressure at the lumbar level was 26 (SD 4) mmHg corresponding to 0.1 (SD 4.1) mmHg at the base of the brain. These results demonstrate that both for venous outflow from the brain and for spinal fluid, the prevailing pressure approaches zero at the base of the brain when humans are upright, which negates that a siphon supports cerebral blood flow.
机译：已经进行了模型研究，以提示虹吸可以在直立位置上支持或不支持脑部血液流动。如果在抬起头部的情况下建立虹吸管，则意味着颈内动脉压力反映出右心房压力减去与大脑的静水压差。这项研究测量了直立位置的脊液压力，仰卧位和坐位的压力和超声测定的颈内静脉大小以及坐着运动期间颈内静脉的压力。当头部抬高到距心脏高度约25 cm时，颈内静脉压力从9.5（SD 2.8）降至0.2（SD 1.0）mmHg [n = 15;值是平均值（SD）; P <0.01]。同样，中心静脉压从6.2（SD 1.8）mmHg降低至0.6（SD 2.6）mmHg（P <0.05）。向上倾斜40度时成像的31条左或右内静脉均未检测到明显的内腔，并且次最大（n = 7）和最大运动（n = 4）不会显着影响颈内静脉压力。当七名受试者坐起时，腰椎水平的脊髓液压力为26（SD 4）mmHg，对应于大脑底部的0.1（SD 4.1）mmHg。这些结果表明，对于从大脑流出的静脉和对于脊髓液而言，当人类直立时，主要的压力在大脑底部接近零，这消除了虹吸支持脑部血流。

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