Spaceflight-associated neuro-ocular syndrome (SANS) involves unilateral or bilateral optic disc edema, widening of the optic nerve sheath, and posterior globe flattening. Due to posterior globe flattening, it is hypothesized that microgravity causes a disproportionate change in intracranial pressure (ICP) relative to intraocular pressure. Countermeasures capable of reducing ICP include thigh cuffs and breathing against inspiratory resistance. Due to the coupling of central venous (CVP) and intracranial pressure, we hypothesized that both ICP and CVP will be reduced during both countermeasures. In four male participants (32±13 yrs) who were previously implanted with Ommaya reservoirs for treatment of unrelated clinical conditions, ICP was measured invasively through these ports. Subjects were healthy at the time of testing. CVP was measured invasively by a peripherally inserted central catheter. Participants breathed through an Impedance Threshold Device (ITD, -7 cm.H₂O) to generate negative intrathoracic pressure for five-mins, and subsequently, wore bilateral thigh cuffs at 30-mmHg for two-mins. Breathing through an ITD reduced both CVP (6±2 vs 3±1 mmHg; P=0.02) and ICP (16±3 vs 12±1 mmHg; P=0.04) compared to the supine posture, which was not observed during the free breathing condition (CVP, 6±2 vs 6±2 mmHg; P=0.87 and ICP, 15±3 vs 15±4 mmHg; P=0.68). Inflation of the thigh cuffs to 30-mmHg caused no meaningful reduction in CVP in all four individuals (5±4 vs 5±4 mmHg; P=0.1), coincident with a minimal reduction in ICP (15±3 vs 14±4 mmHg; P=0.13). The application of inspiratory resistance breathing resulted in reductions in both ICP and CVP, likely due to intrathoracic unloading.

中文翻译：

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通过降低中心静脉压来降低颅内压：评估与航天相关的神经眼综合征的潜在对策。

与太空飞行相关的神经眼综合征（SANS）涉及单侧或双侧视盘水肿，视神经鞘膜增宽和后球变平。由于后球变平，据推测，微重力导致颅内压（ICP）相对于眼压不成比例的变化。能够降低ICP的对策包括大腿袖带和呼吸，以防止吸入阻力。由于中心静脉（CVP）和颅内压的耦合，我们假设在两种对策中ICP和CVP都会降低。在四名男性（32±13岁）患者中，他们先前曾植入Ommaya水库用于治疗无关的临床疾病，通过这些端口对ICP进行了侵入性测量。测试时受试者健康。CVP是通过外围插入的中央导管进行侵入性测量的。参与者通过阻抗阈值设备（ITD，-7 cm.H₂ O）产生5分钟的胸腔负压，随后在30 mmHg处穿上双侧大腿套囊2分钟。与仰卧姿势相比，通过ITD呼吸可降低CVP（6±2 vs 3±1 mmHg; P = 0.02）和ICP（16±3 vs 12±1 mmHg; P = 0.04），这在自由运动期间未观察到呼吸条件（CVP，6±2 vs 6±2 mmHg; P = 0.87和ICP，15±3 vs 15±4 mmHg; P = 0.68）。大腿套囊充气至30mmHg不会使所有四个人的CVP显着降低（5±4 vs 5±4 mmHg; P = 0.1），同时ICP的最小降低（15±3 vs 14±4 mmHg ； P = 0.13）。吸气式阻力呼吸的使用可能导致ICP和CVP的降低，这可能是由于胸腔内卸载引起的。