Use of in-water recompression for decompression illness after deep freediving, a case series
Authors: Nicole Lin, Elaine Yu, Anna Lussier, Emmanuel Gouin, Peter Lindholm
DOI / Source: 10.28920/dhm55.4.376-383
Date: 20 December 2025
Reading level: Intermediate
Why This Matters for Freedivers
This is one of the clearest real-world warnings that serious DCI-like neurological events can happen in freediving, especially around deep, repetitive, high-effort profiles—and that many divers are already self-treating in the water because a chamber isn’t reachable. The big takeaway is simple: surface oxygen early is valuable, but “improvised IWR” can be risky and inconsistent, so deep diving should include a realistic emergency plan (oxygen, decision rules, and evacuation options) rather than hoping symptoms fade.
Synopsis
In-water recompression (IWR) is a controversial idea in scuba: if someone gets decompression illness symptoms, they re-enter the water to a shallow depth (usually around 9 m) and breathe oxygen for a long time as a bridge to getting to a chamber. In freediving, something similar has been happening informally for years—especially in remote locations where a hyperbaric chamber is far away. This paper is a case series that documents those experiences in detail.
The authors interviewed six competitive freedivers and collected 13 incidents where divers developed neurological symptoms after breath-hold diving that were consistent with decompression illness (DCI). They also requested medical records when available. The cases were then grouped by likely mechanism: some looked more like decompression sickness (bubbles forming from dissolved nitrogen after repetitive exposure), some looked more like arterial gas embolism (air entering the arterial circulation after lung overexpansion injury), and some were hard to classify cleanly.
A few patterns stand out:
1) Symptoms can be dramatic and neurological.
These weren’t just vague “post-dive fatigue.” The reported symptom list includes things like one-sided paralysis, slurred speech, inability to walk, facial drooping, severe vertigo, and aphasia (trouble producing language). In several cases, symptoms appeared within minutes after surfacing, which strongly raises suspicion for an embolic-type event.
2) The “provoking factors” will feel very familiar to freedivers.
Across cases, divers often described dehydration, exhaustion/travel fatigue, heavy or repeated lung packing, repetitive deep dives with short surface intervals, exertion after the dive (e.g., pulling up a weight), and in a couple of cases evidence suggestive of lung injury (including coughing blood or lung imaging findings).
3) Oxygen helped a lot—but timing and logistics were everything.
Many cases improved partially or fully with surface oxygen, sometimes within minutes, sometimes over longer periods. The paper repeatedly shows the same practical problem: oxygen was often on shore or not immediately available, causing delays right when minutes matter.
4) IWR was used as self-treatment, with wildly varying “protocols.”
Six cases used IWR at depths ranging roughly 5–25 m for about 20–90 minutes. Some divers did multiple “rounds” because they ran out of oxygen, and symptoms sometimes returned after surfacing—especially when oxygen supply was limited. Four of the IWR-treated cases later received chamber treatment anyway.
5) Outcomes were usually good, but not always.
Most divers recovered fully or near-fully, but at least one case resulted in significant long-term deficits—linked to delays in definitive treatment.
The discussion is where the paper becomes especially useful for the community: it points out that freedivers are already doing IWR without medical oversight, sometimes at deeper-than-recommended depths and sometimes while having symptoms that would normally be considered contraindications (confusion, severe weakness, vomiting risk, etc.). The authors emphasize the real hazards of IWR in freediving settings: drowning risk, oxygen toxicity risk, logistical failure (running out of oxygen), and the false reassurance of “I feel better now” when symptoms can recur.
The paper’s bottom line is not “IWR works” or “IWR doesn’t work.” It’s that DCI-like neurological events after breath-hold diving are real, deep freediving often happens far from chambers, and the community needs realistic, freediving-specific best-practice guidance—especially around oxygen access, when to avoid IWR, and how to prioritize rapid definitive care.
Abstract
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.