Effects of Long-Term Exposure to High G on Blood Oxygen Saturation and Performance

Abstract

The effects of long term exposure to a high g simulated aerial combat maneuver (SACM, or alternating peaks of +4.5Gz to +7.0Gz) were examined using blood oxygen saturation (SAO2) levels and performance measures (RTs, error rates, and comfort ratings). Four different anti-g protection device configurations were evaluated: the standard issue CSU-13 B/P anti-g suit, an experimental retrograde inflation anti-g suit (RIAGS), the RIAGS with capstan sleeves, and the RIAGS with occlusion cuffs. Overall, RIAGS with sleeves allowed subjects to endure much longer times at high g. However, when SA0₂ levels were correlated with time to exhaustion, there were no differences between protective suit configurations. RIAGS with sleeves appeared to lead to a slower decrement in blood oxygen saturation levels during long term exposure, allowing subjects to remain at high g longer. It was also shown that SA0₂ levels “rebounded” to some extent before each of the next +7Gz onsets, but when subjects approached their endurance limits this rebound effect diminished. It seems the longer subjects endured high g, the less able they were to physiologically compensate. The simplest task condition showed an increased in RT when subjects neared their exhaustion point. The more difficult task conditions showed too much variability in RTs to discern any performance patterns. It seemed enough effort and attention was directed to the task to maintain stable performance in the easy condition, but was not enough to maintain performance in the more difficult conditions. Error rates also increased as subjects neared exhaustion, as expected. However, error rates were sensitive to differences among suit configurations, whereas RTs were not. Error rates covaried with time at SACM and comfort ratings. In summary, subjects wearing RIAGS with sleeves withstood high g for longer periods of time, had less error in their performance, and rated the suit most comfortable.