Disclosed herein are methods and devices of obtaining plethysmograph readings and utilizing plethysomography to identify when pilots are about to experience GLOC. Furthermore, in other embodiments, the invention pertains to methods and devices designed to warn a pilot that he/she is about to enter GLOC and/or automatically averting catastrophic damage or injuries by directing a plane being piloted to take predetermined corrective actions. Specifically disclosed is a system embodiment for assisting in the prevention of gravity induced loss of consciousness. The system comprises at least one pulse oximeter probe 10 configured for securing to a central source site of a pilot and to generate signals indicative of blood flow at said central source site, an analyzer unit 58 communicatingly connected to said at least one pulse oximeter probe 10, said analyzer unit comprising at least one processing module 56 configured to determine whether said blood flow is approaching a predefined level, and an aircraft computer 51 communicatingly connected to said analyzer unit 58, said aircraft computer 51 comprising at least one processing module 59 configured to effect a predetermined reaction responsive to said blood flow falling below a predetermined level.
