Tripp L D, Chelette T, Savul S, Widman R A
Systems Research Laboratories/Varidain, Dayton, OH, USA.
Aviat Space Environ Med. 1998 Sep;69(9):869-74.
One of the key factors in maintaining optimal cognitive performance in the high-G environment is the adequate delivery of oxygen to the cerebral tissue. As eye-level blood pressure is compromised at 22 mmHg x G(-1), perfusion to the peripheral cerebral tissues (cerebral cortex) may not be adequate to support the mental demands of flight. This study measured the effect of closed-loop flight simulations (3 min) on cerebral oxygen saturation changes (rSO2), arterial oxygen saturation (SAO2), and heart rate (HR), in both rested (8 h of rest) and sleepless (24 h without sleep) conditions.
Subjects (16; 8 males and 8 females) were subjected to G-exposures via closed-loop flight simulations in a series of four 3-min sorties flown by subjects on the Dynamic Environment Simulator (centrifuge) in either a rested or a sleepless state. Prior to the centrifuge flight, subjects were instrumented with sensors for measurement of arterial oxygen saturation (SAO2) and regional cerebral tissue oxygenation (rSO2). Subjects wore the standard flight suit, boots, CSU-13B/P anti-G suit, and the COMBAT EDGE positive-pressure breathing for G-protection system.
Significant changes in cerebral and arterial oxygen saturation were observed within groups when comparing pretest baselines and minimum values during the test and pre- and post-G rSO2, SAO2, and HR in both the rested and sleepless state, (p # 0.01), respectively, for each group. Comparisons between groups showed women to have significantly smaller regional cerebral cortex oxygen decreases than men (p # 0.01). No significant changes in SAO2, however, were observed between groups. Both men and women showed a slow recovery of rSO2 values to the prebaseline levels.
Sleeplessness had no effect on the rSO2, SAO2, and HR compared with the rested condition. During acceleration, regional cerebral tissue oxygen decreased 13% in men compared with 9% in women. The recovery of cerebral tissue oxygen levels to prebaseline values was retarded somewhat when compared with the recovery response of arterial oxygen saturation.
在高重力环境下维持最佳认知表现的关键因素之一是向脑组织充分输送氧气。由于在22 mmHg×G⁻¹时眼水平血压会受到影响，外周脑组织（大脑皮层）的灌注可能不足以满足飞行中的精神需求。本研究测量了在休息状态（休息8小时）和无睡眠状态（24小时无睡眠）下，闭环飞行模拟（3分钟）对脑氧饱和度变化（rSO₂）、动脉血氧饱和度（SAO₂）和心率（HR）的影响。
16名受试者（8名男性和8名女性）通过在动态环境模拟器（离心机）上进行的一系列四次3分钟的闭环飞行模拟接受重力暴露，受试者处于休息或无睡眠状态。在离心机飞行前，受试者佩戴用于测量动脉血氧饱和度（SAO₂）和局部脑组织氧合（rSO₂）的传感器。受试者穿着标准飞行服、靴子、CSU - 13B/P抗荷服以及用于重力防护系统的COMBAT EDGE正压呼吸装置。
在比较测试前基线与测试期间的最小值以及休息和无睡眠状态下重力暴露前后的rSO₂、SAO₂和HR时，两组内均观察到脑和动脉血氧饱和度有显著变化（p≤0.01）。组间比较显示，女性局部大脑皮层氧含量的降低显著小于男性（p≤0.01）。然而，组间未观察到SAO₂有显著变化。男性和女性的rSO₂值恢复到基线前水平的速度都较慢。
与休息状态相比，无睡眠状态对rSO₂、SAO₂和HR没有影响。在加速过程中，男性局部脑组织氧含量下降了13%，而女性下降了9%。与动脉血氧饱和度的恢复反应相比，脑组织氧水平恢复到基线前值的过程有所延迟。
