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Adaptation of the cardiovascular system to weightlessness: Surprises, paradoxes and implications for deep space missions.
Acta Physiologica ( IF 5.6 ) Pub Date : 2020-01-13 , DOI: 10.1111/apha.13434
Peter Norsk 1
Affiliation  

Weightlessness in space induces a fluid shift from the dependent to the cephalad parts of the body leading to distension of the cardiac chambers and an accumulation of blood in the veins of the head and neck. Surprisingly, central venous pressure (CVP) during the initial hours of spaceflight decreases compared to being horizontal supine on the ground. The explanation is that the thorax is expanded by weightlessness leading to a decrease in inter-pleural pressure (IPP), which exceeds the measured decrease in CVP. Thus, transmural CVP (TCVP = CVP - IPP) is increased indicating an augmented cardiac preload. Simultaneously, stroke volume and cardiac output (CO) are increased by 18%-26% within the initial weeks and more so by 35%-56% during the subsequent months of flight relative to in the upright posture on the ground. Mean arterial pressure (MAP) is decreased indicating a lower systemic vascular resistance (MAP/CO). It is therefore a surprise that sympathetic nerve activity is not suppressed in space and thus cannot be a mechanism for the systemic vasodilation, which still needs to be explored. Recent observations indicate that the fluid shift during long duration (months) flights is associated with increased retinal thickness that sometimes leads to optical disc oedema. Ocular and cerebral structural changes, increases in left atrial size and decreased flows with thrombi formation in the left internal jugular vein have also been observed. This is of concern for future long duration deep space missions because the health implications are unknown.

中文翻译:

使心血管系统适应失重:惊喜,悖论及其对深空任务的影响。

空间失重会引起液体从身体的依附部位转移到头部部位,从而导致心腔扩张,并在头颈部的静脉中积聚血液。出人意料的是,与水平仰卧在地面上相比,航天飞机最初几个小时的中心静脉压(CVP)有所降低。原因是胸腔因失重而膨胀,导致胸膜间压力(IPP)下降,超过了CVP的测量值。因此,透壁CVP(TCVP = CVP-IPP)增加,表明心脏预负荷增加。同时,相对于地面直立姿势,中风量和心输出量(CO)在最初的几周内增加了18%-26%,在接下来的几个月的飞行中增加了35%-56%。平均动脉压(MAP)降低,表明较低的全身血管阻力(MAP / CO)。因此令人惊讶的是,交感神经的活动在空间中没有被抑制,因此不能成为全身性血管舒张的机制,这仍然有待探索。最近的观察表明,长时间(数月)飞行中的液体移位与视网膜厚度增加有关,有时会导致光盘水肿。还观察到眼和脑结构变化,左心房大小增加以及左颈内静脉血流减少并形成血栓。对于未来的长期深空飞行任务,这是令人担忧的,因为其健康影响尚不清楚。因此令人惊讶的是,交感神经的活动在空间中没有被抑制,因此不能成为全身性血管舒张的机制,这仍然有待探索。最近的观察表明,长时间(数月)飞行中的液体移位与视网膜厚度增加有关,有时会导致光盘水肿。还观察到眼和脑结构变化,左心房大小增加以及左颈内静脉血流减少并形成血栓。对于未来的长期深空飞行任务,这是令人担忧的,因为其健康影响尚不清楚。因此令人惊讶的是,交感神经的活动在空间中没有被抑制,因此不能成为全身性血管舒张的机制,这仍然有待探索。最近的观察表明,长时间(数月)飞行中的液体移位与视网膜厚度增加有关,有时会导致光盘水肿。还观察到眼和脑结构变化,左心房大小增加以及左颈内静脉血流减少并形成血栓。对于未来的长时间深空飞行任务,这是一个令人担忧的问题,因为它对健康的影响是未知的。最近的观察表明,长时间(数月)飞行中的液体移位与视网膜厚度增加有关,有时会导致光盘水肿。还观察到眼和脑结构变化,左心房大小增加以及左颈内静脉血流减少并形成血栓。对于未来的长期深空飞行任务,这是令人担忧的,因为其健康影响尚不清楚。最近的观察表明,长时间(数月)飞行中的液体移位与视网膜厚度增加有关,有时会导致光盘水肿。还观察到眼和脑结构变化,左心房大小增加以及左颈内静脉血流减少并形成血栓。对于未来的长期深空飞行任务,这是令人担忧的,因为其健康影响尚不清楚。
更新日期:2020-01-13
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