Ryoo Han C, Sun Hun H, Shender Barry S, Hrebien Leonid
School of Biomedical Engineering, Science and Health Systems, Drexel University, 32nd Chestnut Street, Philadelphia, PA 19104, USA.
Med Eng Phys. 2004 Nov;26(9):745-53. doi: 10.1016/j.medengphy.2004.07.003.
The relationship between human consciousness and oxygen saturation (rSO(2)) in cerebral tissue under high +Gz stress was non-invasively monitored by near-infrared multiple wavelength spectroscopy (NIRS). We studied the drop in rSO(2) levels in human subjects during exposure to various head-to-foot acceleration (+Gz) profiles. These profiles included sustained +Gz plateaus and repeated short duration +Gz pulses of varying duration. The end point in this study was +Gz-induced loss of consciousness (G-LOC). The rSO(2) levels under normal (asymptomatic), almost loss of consciousness (A-LOC) and G-LOC conditions were recorded. Correlations among decrease in rSO(2), +Gz pulse duration, +Gz stress level and incapacitation time (ICAP) after G-LOC were also investigated. It was found that once rSO(2) fell to a certain level, G-LOC occurred. This threshold was repeatable and independent of the +Gz level or duration. It was also observed that the total ICAP after G-LOC was dependent on the length of time that rSO(2) remained below the G-LOC threshold level, i.e. the longer the rSO(2) level remained below the G-LOC induction level, the longer the subject remained unconscious. These results may prove to be useful in designing closed loop control systems for personal protective gear for pilots of high performance aircraft.
通过近红外多波长光谱法（NIRS）对高 +Gz 应激下脑组织中的人类意识与氧饱和度（rSO₂）之间的关系进行了无创监测。我们研究了人类受试者在暴露于各种头脚加速度（+Gz）曲线时 rSO₂ 水平的下降情况。这些曲线包括持续的 +Gz 平台期和不同持续时间的重复短持续时间 +Gz 脉冲。本研究的终点是 +Gz 诱导的意识丧失（G-LOC）。记录了正常（无症状）、几乎意识丧失（A-LOC）和 G-LOC 条件下的 rSO₂ 水平。还研究了 G-LOC 后 rSO₂ 的下降、+Gz 脉冲持续时间、+Gz 应激水平与失能时间（ICAP）之间的相关性。研究发现，一旦 rSO₂ 降至一定水平，就会发生 G-LOC。该阈值是可重复的，且与 +Gz 水平或持续时间无关。还观察到，G-LOC 后的总 ICAP 取决于 rSO₂ 低于 G-LOC 阈值水平的时间长度，即 rSO₂ 水平低于 G-LOC 诱导水平的时间越长，受试者失去意识的时间就越长。这些结果可能在为高性能飞机飞行员设计个人防护装备的闭环控制系统方面具有实用性。
