BACKGROUND: Personnel responding to a distressed submarine incident require information on likely casualty levels and the severity and progression of decompression illness (DCI). Recompression may not be immediately available. First aid oxygen (FAo₂) can be administered; however, there is no direct evidence of its efficacy in this scenario.METHODS: Trials were conducted between 2004 and 2006. Goats exposed to raised pressure for 24 h (‘saturation’) were either returned directly to atmospheric pressure (Phase A, N = 40) or exposed to simulated submarine escape at a depth of 656 ft (200 m; assumed seawater density = 1019.72 kg · m⁻³; Phase B, N = 39). The pressure during saturation was selected to provoke 50% DCI. Cases of DCI were randomly assigned to receive FAo₂ or air.RESULTS: DCI cases were: limb pain in 39 subjects, neurological in 6, respiratory in 4, and pulmonary barotrauma in 1 subject. In Phase A, 5/12 subjects in the FAo₂ group and 0/11 in the air control group achieved permanent resolution of DCI. In Phase B, 6/8 subjects in the FAo₂ group and 5/8 in the air control group achieved permanent resolution. In both Phases, levels of venous gas bubbles reduced sooner with FAo₂. Of three cases of neurological DCI receiving FAo₂, two showed permanent resolution. In total, four cases of respiratory DCI occurred; none of these resolved, with three being treated with FAo₂ and one in the air control.DISCUSSION: Oxygen can be an effective first aid measure for DCI following submarine escape. However, it should not be used as a replacement for recompression therapy.Loveman GAM, Seddon FM, Jurd KM, Thacker JC, Fisher AS. First aid oxygen treatment for decompression illness in the goat after simulated submarine escape. Aerosp Med Hum Perform. 2015; 86(12):1020–1027.