Lower-body negative pressure decreases noninvasively measured intracranial pressure and internal jugular vein cross-sectional area during head-down tilt
Lower-body negative pressure decreases noninvasively measured intracranial pressure and internal jugular vein cross-sectional area during head-down tilt
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DOI：
10.1152/japplphysiol.00091.2017
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发表时间：
2017-07-01
影响因子：
3.3
通讯作者：
Macias, Brandon R.
中科院分区：
文献类型：
--
作者：
Watkins, William;Hargens, Alan R.;Macias, Brandon R.
长期太空飞行会导致约 50% 的宇航员视力发生近乎变化。一些机组人员飞行后腰椎穿刺的脑脊液（CSF）开放压力高达 20.9 毫米汞柱；这些成员表现出视盘水肿。脑脊液通过耳蜗导水管进行交流，影响外淋巴压力和鼓膜运动。我们假设在 15 度头低倾斜 (HDT) 期间 50 mmHg 的下半身负压 (LBNP) 将减轻颈内静脉横截面积 (IJV CSA) 和颅内压 (ICP) 的升高。 15 名健康成年志愿者采取坐位（5 分钟）、仰卧位（5 分钟）、15 度 HDT（5 分钟）和 15 HDT LBNP（10 分钟）姿势进行数据收集。诱发鼓膜位移 (TMD) 可无创地量化 ICP。 IJV CSA 使用标准超声技术测量。从直立坐姿到 15 度 HDT 姿势，ICP 和 IJV CSA 显着增加（P < 0.05），而 LBNP 缓解了这些增加。 25 mmHg 的 LBNP 将 HDT 期间的 ICP（TMD 322.13 +/- 419.17 nl）降低至 232.38 +/- 445.85 nl，而 50 mmHg ICP 进一步降低至 TMD 199.76 +/- 429.69 nl。此外，50 mmHg LBNP 在 15 HDT 期间显着降低 IJV CSA (1.50 +/- 0.33 cm(2)) 至 0.83 +/- 0.42 cm(2)。 LBNP 抵消了 ICP 和 IJV CSA 在微重力过程中经历的向头流体位移升高，如 15 度 HDT 模拟的那样。这些数据提供了定量证据，表明 LBNP 将头液转移到下半身，从而减少了 IJV CSA 和 ICP。新的和值得注意的当前研究提供了新的证据，表明 25 或 50 mmHg 的下半身负压可减少模拟微重力期间的颈静脉池和颅内压。因此，将液体隔离到下半身的航天对策可以减轻头静脉充血和视力障碍。
Longterm spaceflight induces a near visual acuity change in similar to 50% of astronauts. In some crew members, postflight cerebrospinal fluid (CSF) opening pressures by lumbar puncture are as high as 20.9 mmHg; these members demonstrated optic disc edema. CSF communicates through the cochlear aqueduct to affect perilymphatic pressure and tympanic membrane motion. We hypothesized that 50 mmHg of lower-body negative pressure (LBNP) during 15 degrees head-down tilt (HDT) would mitigate elevations in internal jugular vein cross-sectional area (IJV CSA) and intracranial pressure (ICP). Fifteen healthy adult volunteers were positioned in sitting (5 min), supine (5 min), 15 degrees HDT (5 min), and 15 HDT with LBNP (10 min) postures for data collection. Evoked tympanic membrane displacements (TMD) quantified ICP noninvasively. IJV CSA was measured using standard ultrasound techniques. ICP and IJV CSA increased significantly from the seated upright to the 15 degrees HDT posture (P < 0.05), and LBNP mitigated these increases. LBNP at 25 mmHg reduced ICP during HDT (TMD of 322.13 +/- 419.17 nl) to 232.38 +/- 445.85 nl, and at 50 mmHg ICP was reduced further to TMD of 199.76 +/- 429.69 nl. In addition, 50 mmHg LBNP significantly reduced IJV CSA (1.50 +/- 0.33 cm(2)) during 15 HDT to 0.83 +/- 0.42 cm(2). LBNP counteracts the headward fluid shift elevation of ICP and IJV CSA experienced during microgravity as simulated by 15 degrees HDT. These data provide quantitative evidence that LBNP shifts cephalic fluid to the lower body, reducing IJV CSA and ICP.NEW & NOTEWORTHY The current study provides new evidence that 25 or 50 mmHg of lower body negative pressure reduces jugular venous pooling and intracranial pressure during simulated microgravity. Therefore, spaceflight countermeasures that sequester fluid to the lower body may mitigate cephalic venous congestion and vision impairment.