GFAP and injury: To test the hypothesis that a saturation dive might cause injury to the CNS, we selected a number of CNS-specific molecules in blood, Glial fibrillary acidic protein (GFAp), Neurofilament light protein (NfL) and tau protein (tau), the concentrations of which are known to increase in response to different types of brain trauma, including mild traumatic brain injury (Zetterberg 2016), and neuronal stress (Evered 2018, Sato 2018).