On tracking the course of cerebral oxygen saturation and pilot performance during gravity-induced loss of consciousness.
OBJECTIVE
The aim of this study was to track the course of cerebral tissue oxygen saturation (rSO2) and pilot performance during an episode of gravity-induced loss of consciousness (GLOC).


BACKGROUND
GLOC, a major problem facing pilots of high-performance aircraft, is brought about by a sudden reduction in rSO2 as a result of increased +Gz force. It consists of 24 s of complete functional impairment followed by a prolonged period of performance recovery. This study tested the hypothesis that delayed recovery in GLOC is caused by a slow return of rSO2 following removal of the g-force that induced the episode.


METHODS
GLOC was induced in U.S. Air Force personnel via a centrifuge with math and tracking tasks emulating flight performance. A near-infrared spectroscopy unit provided the rSO2 measure.


RESULTS
Declines in rSO2 from baseline pinpointed when pilots would cease active flight control and when GLOC would set in. Counter to expectation, rSO2 returned to baseline levels shortly after the centrifuge came to a complete stop following GLOC onset. Nevertheless, performance deficits continued for 49.45 s thereafter.


CONCLUSIONS
The prolonged performance recovery time in GLOC cannot be attributed to delays in the return of rSO2. This finding explains why previous ergonomic efforts to shorten the duration of GLOC episodes by increasing the rate of return of rSO2 have not been fruitful. Evidently, another approach is needed.


CONCLUSIONS
Such an approach might use the close linkage between loss of rSO2, performance deterioration, and GLOC onset to develop a warning system that would permit pilots to take effective action to avoid GLOC incapacitation.
Tripp
Lloyd D
LD
Biosciences and Performance Division, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA. lloyd.tripp@wpafb.af.mil
Warm
Joel S
JS
Matthews
Gerald
G
Chiu
Peter Y
PY
Bracken
R Bruce
RB
D000054:Acceleration / Q000009:adverse effects; D000328:Adult; D000337:Aerospace Medicine; D002560:Cerebrovascular Circulation; D006804:Ergonomics; D005260:Female; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D002534:Hypoxia, Brain / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008889:Military Personnel; D009048:Motor Skills; D010100:Oxygen / Q000378:metabolism*; D020127:Recovery of Function; D014474:Unconsciousness / Q000209:etiology / Q000503:physiopathology*
D010100:Oxygen