Use of in-water recompression for decompression illness after deep freediving: a case series.

Introduction: There are increasing anecdotal reports of in-water recompression in freedivers who surface with neurological symptoms, likely suffering from decompression illness (DCI). Given the remote locations where many cases occurred, divers often struggled to access medical care, including the gold-standard hyperbaric oxygen treatment (HBOT), thus resorting to in-water recompression (IWR). Currently, IWR guidelines have only been discussed for scuba and surface supplied divers in specific scenarios, with protocols prescribing oxygen breathing at depths ≤ 9 metres maximum for around 1-3 hours. Methods: We conducted detailed interviews with six competitive freedivers on signs, symptoms, management, and resolution of 13 cases of DCI. We additionally requested records of medical evaluation and treatment, with their consent. Results: Three cases were suggestive of decompression sickness, six were consistent with arterial gas embolism, and four were ambiguous. Six cases were treated with IWR for 20-90 min at 5-25 metres with partial to complete resolution of symptoms. Four of these cases received HBOT afterwards. One diver reported significant permanent disability. Divers made several regimen changes after these incidents, including staying well-hydrated, reducing lung-packing, slowing their ascent rate, and/or employing prophylactic IWR when diving beyond a specified depth. Conclusions: Given the remote locations of many incidents, freedivers often faced challenges in accessing HBOT. Self-treatment with IWR was widely used, either as a bridge to HBOT or as a standalone remedy. IWR poses potential risks, especially at the deeper depths reported in this study. This treatment modality is being utilised sometimes without medical oversight and recommended guidelines for IWR for freedivers should be developed.