Marshall-Goebel Karina, Stevens Brian, Rao Chethan Venkatasubba, Suarez Jose I, Calvillo Eusebia, Arbeille Philippe, Sangi-Haghpeykar Haleh, Donoviel Dorit B, Mulder Edwin, Bershad Eric M
Aerosp Med Hum Perform. 2018 Apr 1;89(4):351-356. doi: 10.3357/AMHP.4934.2018.
Cerebral hemodynamics and venous outflow from the brain may be altered during exposure to microgravity or head-down tilt (HDT), an analog of microgravity, as well as by increased ambient CO2 exposure as experienced on the International Space Station.
Six healthy subjects underwent baseline tilt table testing at 0°, 6°, 12°, 18°, 24°, and 30° HDT. The right internal jugular (IJ) vein cross-sectional area (CSA) was measured at four intervals from the submandibular to the clavicular level and IJ volume was calculated. Further measurements of the IJ vein were made after ∼26 h of 12° HDT bed rest with either ambient air or 0.5% CO2 exposure, and plasma and blood volume were assessed after 4 h, 24 h, and 28.5 h HDT.
IJ vein CSA and volume increased with progressively steeper HDT angles during baseline tilt table testing, with more prominent filling of the IJ vein at levels closer to the clavicle. Exposure to 26 h of 12° HDT bed rest with or without increased CO2, however, had little additional effect on the IJ vein. Further, bed rest resulted in a decrease in plasma volume and blood volume, although changes did not depend on atmospheric conditioning or correlate directly with changes in IJ vein CSA or volume.
The hydrostatic effects of HDT can be clearly determined through measurement of the IJ vein CSA and volume; however, IJ vein dimensions may not be a reliable indicator of systemic fluid status during bed rest.Marshall-Goebel K, Stevens B, Rao CV, Suarez JI, Calvillo E, Arbeille P, Sangi-Haghpeykar H, Donoviel DB, Mulder E, Bershad EM, the SPACECOT Investigators Group. Internal jugular vein volume during head-down tilt and carbon dioxide exposure in the SPACECOT Study. Aerosp Med Hum Perform. 2018; 89(4):351-356.
在暴露于微重力环境或头低位倾斜（HDT，微重力模拟环境）期间，以及在国际空间站所经历的环境二氧化碳暴露增加时，脑血流动力学和脑静脉流出可能会发生改变。
6名健康受试者在0°、6°、12°、18°、24°和30°头低位倾斜下进行基线倾斜台测试。在从下颌骨到锁骨水平的四个间隔处测量右颈内静脉（IJ）横截面积（CSA），并计算IJ容积。在12°头低位倾斜卧床休息约26小时后，分别在空气环境或0.5%二氧化碳暴露条件下对IJ静脉进行进一步测量，并在头低位倾斜4小时、24小时和28.5小时后评估血浆和血容量。
在基线倾斜台测试期间，IJ静脉CSA和容积随着头低位倾斜角度逐渐变陡而增加，在更靠近锁骨的水平处IJ静脉充盈更明显。然而，在有或没有二氧化碳增加的情况下，12°头低位倾斜卧床休息26小时对IJ静脉几乎没有额外影响。此外，卧床休息导致血浆容量和血容量减少，尽管变化不取决于大气条件，也与IJ静脉CSA或容积的变化没有直接关联。
通过测量IJ静脉CSA和容积可以清楚地确定头低位倾斜的流体静力效应；然而，IJ静脉尺寸可能不是卧床休息期间全身液体状态的可靠指标。
马歇尔 - 戈贝尔K，史蒂文斯B，饶CV，苏亚雷斯JI，卡尔维洛E，阿贝耶尔P，桑吉 - 哈格佩卡尔H，多诺维尔DB，穆德E，伯沙德EM，太空舱研究调查组。太空舱研究中头低位倾斜和二氧化碳暴露期间的颈内静脉容积。航空航天医学与人类表现。2018年；89(4):351 - 356。
