Department of Diagnostic Imaging and Intervention, McGovern Medical School, UTHealth Houston, Houston, Texas, United States.
Center for Clinical and Translational Sciences, McGovern Medical School, UTHealth Houston, Houston, Texas, United States.
J Appl Physiol (1985). 2024 Nov 1;137(5):1071-1081. doi: 10.1152/japplphysiol.00441.2024. Epub 2024 Sep 12.
Long-duration spaceflight is associated with pathophysiological changes in the intracranial compartment hypothetically linked to microgravity-induced headward fluid shift. This study aimed to determine whether daily artificial gravity (AG) sessions can mitigate these effects, supporting its application as a countermeasure to spaceflight. Twenty-four healthy adult volunteers (16 men) were exposed to 60 days of 6° head-down tilt bed rest (HDTBR) as a ground-based analog of chronic headward fluid shift. Subjects were divided equally into three groups: no AG (control), daily 30-min intermittent AG (iAG), and daily 30-min continuous (cAG). Internal carotid artery (ICA) stroke volume (ICA), ICA resistive index (ICA), ICA flow rate (ICA), aqueductal cerebral spinal fluid flow velocity (CSF), and intracranial volumetrics were quantified at 3 T. MRI was performed at baseline, 14 and 52 days into HDTBR, and 3 days after HDTBR (recovery). A mixed model approach was used with intervention and time as the fixed effect factors and the subject as the random effect factor. Compared with baseline, HDTBR was characterized by expansion of lateral ventricular, white matter, gray matter, and brain + total intracranial cerebral spinal fluid volumes, increased CSFv, decreased ICA, and decreased ICA by 52 days into HBTBR (All s < 0.05). ICA was only increased 14 days into HDTBR ( < 0.05). Neither iAG nor cAG significantly affected measurements compared with HDTBR alone, indicating that 30 min of daily exposure was insufficient to mitigate the intracranial effects of headward fluid shift. Greater AG session exposure time, gravitational force, or both are suggested for future countermeasure research. Brief exposure to continuous or intermittent artificial gravity via short-arm centrifugation was insufficient in mitigating the intracranial pathophysiological effects of the headward fluid shift simulated during head-down tilt bed rest (HDTBR). Our results suggest that greater centrifugation session duration, gravitational force, or both may be required to prevent the development of spaceflight-associated neuro-ocular syndrome and should be considered in future ground-based countermeasure studies.
长时间的太空飞行会导致颅内压生理变化，这与微重力引起的头部液流转移有关。本研究旨在确定每日人工重力（AG）是否可以减轻这些影响，从而支持其作为对抗太空飞行的一种手段。24 名健康成年志愿者（16 名男性）接受了 60 天的 6°头低位卧床休息（HDTBR），作为慢性头部液流转移的地面模拟。受试者被平均分为三组：无 AG（对照组）、每日 30 分钟间歇性 AG（iAG）和每日 30 分钟连续 AG（cAG）。在 3T 上测量颈内动脉（ICA）血流量（ICA）、ICA 阻力指数（ICA）、ICA 流速（ICA）、导水管脑脊髓液流速（CSF）和颅内容积。MRI 在基线、HDTBR 第 14 天和第 52 天以及 HDTBR 后 3 天（恢复期）进行。采用混合模型方法，干预和时间为固定效应因素，受试者为随机效应因素。与基线相比，HDTBR 表现为侧脑室、白质、灰质和脑+总颅内脑脊液体积扩大，CSFv 增加，ICA 减少，52 天 HBTBR 时 ICA 减少（均 s < 0.05）。ICA 仅在 HDTBR 第 14 天增加（<0.05）。与单独 HDTBR 相比，iAG 和 cAG 均未显著影响测量结果，表明每天 30 分钟的暴露时间不足以减轻头部液流转移引起的颅内影响。建议未来的对策研究增加 AG 治疗时间、重力或两者兼而有之。通过短臂离心机短暂暴露于连续或间歇人工重力不足以减轻头低位卧床休息（HDTBR）模拟的头部液流转移引起的颅内病理生理效应。我们的结果表明，可能需要更长的离心治疗时间、更大的重力或两者兼而有之，以防止发生与太空飞行相关的神经眼综合征，并应在未来的地面对策研究中考虑。
