PDF(Pubmed)
Abstract：
Onboard oxygen-generating systems (OBOGSs) provide increased inspired oxygen (FiO2) to mitigate the risk of neurologic injury in high altitude aviators. OBOGSs can deliver highly variable oxygen concentrations oscillating around a predetermined FiO2 set point, even when the aircraft cabin altitude is relatively stable. Steady-state exposure to 100% FiO2 evokes neurovascular vasoconstriction, diminished cerebral perfusion, and altered electroencephalographic activity. Whether non-steady-state FiO2 exposure leads to similar outcomes is unknown. This study characterized the physiologic responses to steady-state and non-steady-state FiO2 during normobaric and hypobaric environmental pressures emulating cockpit pressures within tactical aircraft. The participants received an indwelling radial arterial catheter while exposed to steady-state or non-steady-state FiO2 levels oscillating ± 15% of prescribed set points in a hypobaric chamber. Steady-state exposure to 21% FiO2 during normobaria produced arterial blood gas values within the anticipated ranges. Exposure to non-steady-state FiO2 led to PaO2 levels higher upon cessation of non-steady-state FiO2 than when measured during steady-state exposure. This pattern was consistent across all FiO2 ranges, at each barometric condition. Prefrontal cortical activation during cognitive testing was lower following exposure to non-steady-state FiO2 >50% and <100% during both normobaria and hypobaria of 494 mmHg. The serum analyte levels (IL-6, IP-10, MCP-1, MDC, IL-15, and VEGF-D) increased 48 h following the exposures. We found non-steady-state FiO2 levels >50% reduced prefrontal cortical brain activation during the cognitive challenge, consistent with an evoked pattern of neurovascular constriction and dilation.
摘要：
机载制氧系统（OBOGS）提供增加的吸入氧气（FiO2），以减轻高海拔飞行员的神经损伤风险。OBOGS可以提供在预定的FiO2设定点附近振荡的高度可变的氧气浓度，即使飞机机舱高度相对稳定。稳态暴露于100%FiO2引起神经血管收缩，脑灌注减少,和脑电图活动改变。非稳态FiO2暴露是否会导致类似的结果尚不清楚。这项研究表征了在模拟战术飞机内驾驶舱压力的常压和低压环境压力期间对稳态和非稳态FiO2的生理反应。参与者在暴露于低压舱中的稳态或非稳态FiO2水平振荡±15％的规定设定值时，接受了留置的radial动脉导管。在正常范围内，稳态暴露于21％的FiO2会产生预期范围内的动脉血气值。暴露于非稳态FiO2导致在非稳态FiO2停止时的PaO2水平高于在稳态暴露期间测量的PaO2水平。这种模式在所有FiO2范围内都是一致的，在每种气压条件下。在暴露于非稳态FiO2>50％和<100％后，认知测试期间的前额叶皮层激活较低。血清分析物水平(IL-6，IP-10，MCP-1，MDC，IL-15和VEGF-D）在暴露后48小时增加。我们发现，在认知挑战期间，非稳态FiO2水平>50％会降低前额叶皮质脑激活，与神经血管收缩和扩张的诱发模式一致。
