Correlation of NIRS determined cerebral oxygenation with severity of pilot +Gz acceleration symptoms.

Pilots commonly experience decreased peripheral vision, confusion & disorientation, and/or unconsciousness when exposed to high +Gz acceleration. We correlated NIRS determined delta Hb, delta HbO2, and delta TotalHb with the resultant +Gz stress symptoms that subjects reported after experiencing a 6 to 10 +Gz amplitude pulse. During the hyperemic response phase following the +Gz pulses, an increase of the averaged peak values of delta HbO2 and delta TotalHb as a function of the severity of the subjects' symptoms was observed. Significant increases were found for the averaged peak values of delta HbO2 and delta TotalHb between high vision loss, confusion and disorientation while remaining conscious (A-LOC), and unconsciousness (G-LOC). The results suggest that the confusion and disorientation associated with A-LOC is physiologically based and that A-LOC is an intermediate +Gz stress symptom between high peripheral vision loss and G-LOC. Like G-LOC, pilots who experience A-LOC symptoms momentarily do not have full control of their aircraft.