New decompression gas CF₄/O₂: reducing DCS risk and ameliorating injuries in male rats

Decompression sickness (DCS) remains a major risk in diving. Prolonging decompression reduces inert gas load but increases operation time and underwater exposure. We tested a carbon tetrafluoride-oxygen mixture (CF₄/O₂) as a decompression gas in two rat decompression protocols: 6 ATA compressed air and 9 ATA helium-oxygen (heliox). Switching to CF₄/O₂ 10 min before decompression significantly reduced DCS incidence in both protocols: air, 68% (19/28) to 11% (3/28); heliox, 68% (15/22) to 18% (4/22). Mortality was significantly reduced in the compressed-air protocol (29% [8/28] to 0 [0/28], P = 0.004) but not in the heliox protocol (14% [3/22] to 0 [0/22], P = 0.233). Echocardiography showed fewer or no intracardiac bubbles after CF₄/O₂. In the heliox protocol, CF₄/O₂ significantly modulated some pulmonary function parameters; in the compressed-air protocol, pulmonary function changes were time-dependent and did not differ significantly between groups. CF₄/O₂ also reduced lung inflammation, endothelial injury, and histological damage in both protocols. In a 28-day repeated hyperbaric exposure protocol assessing selected serum biochemical endpoints, CF₄/O₂ did not increase serum alanine aminotransferase, aspartate aminotransferase, creatinine or urea; however, this protocol did not include post-exposure histopathology or haematology, so safety conclusions are limited to the measured endpoints. These findings support the tested CF₄/O₂ gas-switching strategy under the specific conditions used. Shorter decompression protocols were not tested, and shortening decompression time remains a potential application rather than a demonstrated outcome.