Abstract：
During spaceflight, fluids shift headward, causing internal jugular vein (IJV) distension and altered hemodynamics, including stasis and retrograde flow, that may increase the risk of thrombosis. This study\'s purpose was to determine the effects of acute exposure to weightlessness (0-G) on IJV dimensions and flow dynamics. We used two-dimensional (2-D) ultrasound to measure IJV cross-sectional area (CSA) and Doppler ultrasound to characterize venous blood flow patterns in the right and left IJV in 13 healthy participants (6 females) while 1) seated and supine on the ground, 2) supine during 0-G parabolic flight, and 3) supine during level flight (at 1-G). On Earth, in 1-G, moving from seated to supine posture increased CSA in both left (+62 [95% CI: +42 to 81] mm2, P < 0.0001) and right (+86 [95% CI: +58 to 113] mm2, P < 0.00012) IJV. Entry into 0-G further increased IJV CSA in both left (+27 [95% CI: +5 to 48] mm2, P = 0.02) and right (+30 [95% CI: +0.3 to 61] mm2, P = 0.02) relative to supine in 1-G. We observed stagnant flow in the left IJV of one participant during 0-G parabolic flight that remained during level flight but was not present during any imaging during preflight measures in the seated or supine postures; normal venous flow patterns were observed in the right IJV during all conditions in all participants. Alterations to cerebral outflow dynamics in the left IJV can occur during acute exposure to weightlessness and thus, may increase the risk of venous thrombosis during any duration of spaceflight.NEW & NOTEWORTHY The absence of hydrostatic pressure gradients in the vascular system and loss of tissue weight during weightlessness results in altered flow dynamics in the left internal jugular vein in some astronauts that may contribute to an increased risk of thromboembolism during spaceflight. Here, we report that the internal jugular veins distend bilaterally in healthy participants and that flow stasis can occur in the left internal jugular vein during acute weightlessness produced by parabolic flight.
摘要：
在太空飞行期间，液体向前移动，引起颈内静脉（IJV）扩张和血流动力学改变，包括停滞和逆行流，这可能会增加血栓形成的风险。这项研究的目的是确定急性暴露于失重（0-G）对IJV尺寸和流动动力学的影响。我们使用二维（2-D）超声测量IJV横截面积（CSA）和多普勒超声来表征13名健康参与者（6名女性）的右侧和左侧IJV的静脉血流模式，2）在0-G抛物线飞行期间仰卧，和3)平飞期间仰卧(1-G)。在地球上,在1-G中，从坐位到仰卧位的移动增加了左侧(+62[95%CI:+42~81]mm2,P<0.0001)和右侧(+86[95%CI:+58~113]mm2,P<0.00012)的CSA。进入0-G时，相对于1-G仰卧，左侧（+27[95％CI：+5至48]mm2，P=0.02）和右侧（+30[95％CI：+0.3至61]mm2，P=0.02）的IJVCSA进一步增加。我们观察到一名参与者在0-G抛物线飞行期间左IJV的停滞流量在水平飞行期间仍然存在，但在坐姿或仰卧姿势的飞行前措施期间的任何成像过程中都不存在；在所有参与者的所有情况下，在右IJV中观察到正常的静脉血流模式。在急性暴露于失重期间，左脑脑流出动力学可能发生改变，因此，在任何航天期间都可能增加静脉血栓形成的风险。新的和注意在失重期间血管系统中没有静水压力梯度和组织重量的损失导致一些宇航员的左颈内静脉中的血流动力学改变,这可能导致在太空飞行期间血栓栓塞的风险增加。这里,我们报告说，健康参与者的颈内静脉双侧扩张，在抛物线飞行产生的急性失重期间，左颈内静脉可发生血流停滞。
