Technical diving accidents in France: a 15-year retrospective study reporting a high prevalence of musculoskeletal decompression sickness

Introduction: Technical diving, involving rebreathers and/or helium-based gas mixtures for deeper and longer dives, may influence risk and clinical presentation of injuries due to helium's properties, equipment constraints, or exposure conditions. This study aims to describe the specific characteristics of this accidentology. Methods: A retrospective study was conducted across five French coastline hyperbaric units. Medical records of technical divers presenting with decompression sickness (DCS), immersion pulmonary oedema (IPO), or gas-toxicity between 2010 and 2024 were reviewed. Results: 127 technical divers were included, three declined participation, leaving 124 cases for analysis. DCS was the most frequent condition (n = 105) followed by IPO (n = 16) and gas toxicity (n = 3). Median age was 45 [IQR 37-53] years, and 113 (91%) were male. Rebreathers were used in 94 (75.8%) cases and helium-based mixtures in 77 (62%). Previous diving-related accidents were reported in 36 (29%) cases. IPO occurred mainly after shallower dives in wetsuits and was frequently associated with procedural errors. Among DCS cases isolated musculoskeletal DCS predominated (n = 36), whereas spinal involvement was less frequent. When indicated, median recompression delay was 238 [IQR 135-555] minutes. Unfavourable outcomes occurred in 26 (25%) DCS cases, primarily with bone or inner-ear involvement. Conclusions: Technical diving accidents exhibit distinct patterns from recreational diving, notably greater musculoskeletal involvement and a possible increased risk of dysbaric osteonecrosis (DON). Current evidence does not support different management, but the risk of potential initially silent bone lesions should not be overlooked. Further research on helium-related risks and hyperbaric treatment's role in DON prevention is needed.