NIRS monitoring of pilots subjected to +Gz acceleration and G-induced loss of consciousness (G-LOC).

With the increasing maneuverability of modern aircraft, there is an increased frequency of pilots losing consciousness due to high +Gz acceleration. This phenomena is defined as "G-induced loss of consciousness" (G-LOC). We used an NIRS system of our design to monitor cerebral oxygenation changes of pilots subjected to high +Gz acceleration and G-LOC. During the +Gz pulse, delta HbO2, and delta TotalHb decreased, with lesser changes of delta Hb. The maximum decrease of delta HbO2 and delta TotalHb usually occurred at the onset of G-LOC. After G-LOC, delta HbO2 and delta TotalHb increased rapidly for the first few seconds, beginning the reactive hyperemic recovery phase. delta HbO2 and delta TotalHb peaked, and then began to decrease towards baseline. The subjects were unconscious for 3-10 seconds after the onset of G-LOC. Upon returning to consciousness, the subjects were disoriented for another 4-11 seconds. NIRS provides an additional means of studying physiological mechanisms leading to and recovery from G-LOC.