Hyperbaric Decompression Chamber: How Recompression Treats the Bends

The short answer: A hyperbaric decompression chamber is, in treatment terms, a recompression chamber: the injured diver is pressed back to 2.8 ATA and breathes 100% oxygen on the U.S. Navy Treatment Table 6, a nearly five-hour protocol. Recompression is the definitive, FDA-cleared treatment for decompression sickness.

Decompression sickness (DCS), the condition divers call “the bends,” is where hyperbaric medicine began. It is also one of the few indications where every US authority agrees: the FDA has cleared chambers for it, the UHMS lists it as approved indication #5, and Medicare covers it under NCD 20.29. Our hub guide to what HBOT is actually FDA-cleared to treat maps all three lists; this article goes deep on the diving indication itself: what the chamber is, what the bubbles do, how the treatment tables work, and what the outcome data show.

Disclosure: Superhuman Chambers manufactures and sells hyperbaric chambers for wellness operators and home use. Decompression sickness treatment is an emergency medical procedure performed in clinical and military hyperbaric facilities; it is not a wellness application of our equipment. This article summarizes published evidence for education only and is not medical advice.

What a hyperbaric decompression chamber actually is

The search term bundles together three overlapping pieces of hardware, and untangling them clears up most of the confusion around the topic.

Decompression versus recompression: the word difference that matters

A decompression chamber, in strict diving usage, is a chamber used to bring a diver down in pressure in a controlled way: commercial and saturation divers finish long dives by decompressing in a chamber on the surface instead of hanging in the water. A recompression chamber does the opposite job: it puts an injured diver back up in pressure to crush the bubbles causing DCS, then decompresses them slowly and safely. When a diver with the bends is “put in the chamber,” that is recompression, and the device is a recompression chamber.

A hyperbaric chamber is the broad engineering term: any pressure vessel for human occupancy (built to ASME PVHO standards) that raises ambient pressure above sea level. Hospital hyperbaric departments treat DCS in the same chambers they use for wounds, carbon monoxide poisoning, and the other FDA-cleared indications. So “hyperbaric decompression chamber” is best read as everyday language for a hyperbaric chamber used in diving medicine, and the treatment itself is recompression.

The chamber family, by mission

The distinction between monoplace and multiplace chambers matters most for DCS: a multiplace chamber is pressurized with air while patients breathe oxygen through masks or hoods, with medical staff inside the vessel, which is why it remains the standard platform for sick divers. Monoplace chambers can and do deliver the US Navy tables in selected patients, as the outcome section shows.

Why pressure makes divers sick

The physics is described by Henry’s law: the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas above it. At depth, a diver’s breathing gas is delivered at ambient pressure, so body tissues load with dissolved nitrogen in proportion to depth and time. Ascend slowly, and the excess gas washes out through the lungs in an orderly way. Ascend too fast, and the tissues become supersaturated: nitrogen comes out of solution as bubbles in blood and tissue, the same way CO2 fizzes out of a freshly opened bottle.

Those bubbles injure in two ways. They mechanically obstruct small vessels, and they trigger an inflammatory and clotting response at the blood-bubble interface, compounding the ischemia. The clinical picture is grouped by severity:

• Type I DCS (“the bends” proper, about 85% of cases): joint and muscle pain, classically the shoulder, plus skin mottling (cutis marmorata) and lymphatic swelling.
• Type II DCS: neurological involvement (numbness, weakness, bladder dysfunction, cognitive change), inner-ear DCS (vertigo, hearing loss), and the rare, life-threatening pulmonary form called “the chokes.”
• Arterial gas embolism (AGE) is a separate mechanism: lung overexpansion on ascent tears alveoli and forces gas directly into the arterial circulation. Clinicians group DCS and AGE under one umbrella, decompression illness (DCI), because the first aid and the definitive treatment are identical.

DCS is genuinely rare. DAN’s Project Dive Exploration measured an incidence of 3.4 cases per 10,000 dives in recreational diving, and published estimates cluster around 3 per 10,000 for sport divers, with commercial diving higher at 1.5–10 per 10,000 dives. Timing is fast: in the large Turkish series, 47% of divers were symptomatic during ascent or within 10 minutes of surfacing, and 87% within the first hour; an Israeli series found 98% of cases present within 24 hours. A diver who feels unwell after a dive should treat it as DCS until a diving-medicine physician says otherwise.

The original proven indication

The disease predates scuba. Workers digging bridge foundations inside pressurized caissons in the 1860s and 1870s came out of the worksites with joint pain, paralysis, and sometimes death, and the condition was named caisson disease. Paul Bert’s 1878 La Pression Barométrique identified dissolved-gas bubbles as the mechanism and predicted both the cure (slow decompression) and the emergency treatment (put the patient back under pressure). Recompression “medical locks” on tunnel projects in the 1880s and 1890s confirmed it in practice, and the US Navy spent the 20th century turning the idea into standardized treatment tables.

That century of refinement is why DCS sits so comfortably on every modern list. It is one of the 13 FDA-cleared conditions for hyperbaric chambers, indication #5 in the UHMS Hyperbaric Medicine Indications Manual (15th edition, 2023), and covered by Medicare under NCD 20.29 as “decompression illness.” Among the indications in the FDA-cleared indications guide, it is the one where the chamber is not an adjunct to other care: for DCS, recompression is the treatment.

How recompression treatment works

The standard of care worldwide is the U.S. Navy Treatment Table 6 (USN TT6), published in the US Navy Diving Manual:

• The chamber is compressed to 60 feet of seawater (18 msw), equivalent to 2.8 ATA.
• The patient breathes 100% oxygen, interspersed with scheduled air breaks that reduce the risk of oxygen toxicity.
• Total treatment time is about 4 hours 45 minutes, and the table can be extended with additional oxygen periods at 60 or 30 feet if symptoms are not resolving.
• Treatment Table 5, a shorter roughly two-hour version, covers pain-only DCS that resolves completely within 10 minutes at treatment depth; anything more severe or slower to respond gets Table 6.

Three mechanisms do the work. First, Boyle’s law: at 2.8 ATA, bubble volume shrinks to roughly a third of its surface size, immediately relieving mechanical obstruction. Second, the oxygen window: breathing pure oxygen drives blood nitrogen partial pressure toward zero, creating a steep diffusion gradient that pulls nitrogen out of the bubbles and into the lungs. Third, hyperoxia itself: dissolved plasma oxygen at treatment pressure re-oxygenates ischemic tissue and blunts the inflammatory cascade at the blood-bubble interface. Treatment continues, sometimes over repeated daily sessions, until symptoms plateau.

Oxygen at 2.8 ATA is a drug with a real side effect: central nervous system oxygen toxicity can cause seizures mid-treatment. The largest modern series, 1,000 TT6 treatments over 30 years in Western Australia, recorded four seizures (0.59% in the multiplace chamber, zero in 331 monoplace treatments), all self-limited. It is one reason these treatments belong in staffed medical facilities, not improvised settings.

What the outcome data show

There are no placebo-controlled trials of recompression for DCS, and there never will be: withholding the definitive treatment would be unethical. The evidence is a deep stack of case series and database analyses, and it points in a consistent direction.

Three lessons fall out of the table. Fast is best: military data with sub-two-hour delays show resolution rates above 90%, and first-aid oxygen meaningfully improves the odds. Late is not hopeless: two independent series, 750 patients combined, found recompression still works days after the dive, so divers should be treated even after long delays rather than written off. And severity is destiny: the biggest determinant of residual injury is how hard the diver was hit initially, which is why severe neurological DCS keeps a roughly one-in-four incomplete-recovery rate even with world-class response times.

Where treatment actually happens

The protocol for a suspected case is fixed: call emergency medical services first, then call DAN (Divers Alert Network) at +1-919-684-9111. DAN’s medics coordinate with the treating facility around the clock and route patients to chambers that accept diving casualties. Two practical realities sit behind that advice. Showing up unannounced at the nearest hyperbaric chamber is a mistake: many US hospital chambers run elective wound-care schedules, are not staffed after hours or on weekends, and do not accept diving emergencies at all. DAN has documented a shrinking number of North American chambers willing to take diving casualties, particularly outside business hours, which makes the hotline’s coordination role the difference between a four-hour and a fourteen-hour delay.

Remote operations plan around this. Commercial dive contractors and military units station transportable recompression chambers at the dive site, and remote dive resorts maintain referral agreements with regional multiplace facilities. For severe cases, the multiplace chamber remains the definitive platform: medical tenders inside the vessel can manage airways, IVs, and deteriorating patients during a five-hour table, and multilock designs let staff and equipment pass in and out under pressure. For stable patients, the monoplace evidence above shows clinical chambers deliver TT6 safely.

Prevention and first aid

Recompression works, but the entire diving safety system exists to keep divers out of the chamber:

• Dive conservatively: stay well within the no-decompression limits of your tables or computer, and treat deep, cold, or repetitive dives with extra margin.
• Control the ascent: slow ascent rates plus a safety stop of 3–5 minutes at 3–5 meters on every dive.
• Mind the surface interval: follow flying-after-diving guidance (DAN recommends a minimum of 12 hours after a single no-stop dive, 18 hours after repetitive dives, and substantially longer after decompression dives).
• Manage the cofactors: hydration, rest, no alcohol around diving, and honest assessment of fitness; recurrent DCS on conservative profiles warrants a dive-medicine workup, including evaluation for a patent foramen ovale.

If symptoms appear anyway, the first aid is 100% oxygen at the highest available concentration, started immediately and continued through transport; the Longphre analysis shows it improves recompression outcomes even hours later. Lay the diver flat and horizontal, give oral fluids if fully conscious, keep an unpressurized evacuation below roughly 300 meters (1,000 feet) of altitude, and get EMS and DAN on the phone. Do not put the diver back in the water: in-water recompression is an option of last resort for trained teams in genuinely remote locations, because an oxygen seizure underwater means drowning.

Limitations and open questions

Start with what is solid: the indication rests on 150 years of mechanistic understanding, standardized military protocols, regulatory clearance, medical-society approval, Medicare coverage, and outcome series totaling thousands of patients, with resolution rates above 90% when treatment is fast.

The honest caveats follow. The evidence base is entirely observational: no randomized trial will ever compare recompression against sham, so effect sizes come from case series with their inherent biases. The delay-versus-outcome relationship is confounded: divers with severe symptoms get evacuated fastest, which makes delayed treatment look artificially harmless in some series; the correct reading is “late treatment still helps,” never “delay is safe.” Optimal table selection for unusual presentations (deep mixed-gas technical dives, inner-ear DCS, altitude DCS) remains expert territory, and adjunctive drug therapy has no established role. Finally, the access problem is unsolved: treatment outcomes in the literature come from organized systems with chambers on standby, while the real-world North American chamber network available to recreational divers continues to thin out.

What this means for wellness operators

This is the emergency-medicine end of the hyperbaric family tree, and it asks for precision rather than promotion.

Keep the boundary explicit. DCS treatment is an emergency procedure at 2.8 ATA under physician and diving-medicine supervision, delivered in staffed clinical or military chambers. Nothing about it maps onto a wellness service, and no wellness chamber should ever be described, even obliquely, as suitable for treating an injured diver. The accurate statement is the proud one: the same physics that makes clinical hyperbaric medicine work is what your clients are reading about when they search this term, and operators who explain the difference correctly earn trust with a medically literate audience.

Know the referral, not the remedy. Operators in coastal and dive-travel markets occasionally meet clients who dive. The useful knowledge is the emergency protocol: EMS first, DAN at +1-919-684-9111 second, 100% oxygen and horizontal rest meanwhile. Having that on a staff reference card is a safety asset that costs nothing.

Let the equipment classes speak for themselves. The entire DCS literature runs at 2.8 ATA on hard-shell medical systems, a pressure class apart from soft-shell wellness units; our guide to hyperbaric chamber pressure levels maps exactly where each equipment class sits and why clinical indications demand clinical pressures. Operators building a serious, evidence-anchored wellness program should understand that map when they evaluate hardware: a hard-shell system like the Superhuman T2 exists in the engineering lineage this article describes, designed for the kind of structural and pressure integrity that what makes a chamber medical-grade lays out, even though its job is wellness rather than emergency recompression. For the sister proven indications where elective clinical HBOT does apply, our wound healing evidence guide makes the same sourced distinction.

References

1. Vann RD, Butler FK, Mitchell SJ, Moon RE. Decompression illness. Lancet 2011;377(9760):153-164. PMID: 21215883. DOI: 10.1016/S0140-6736(10)61085-9.
2. US Department of the Navy. US Navy Diving Manual, Revision 7. NAVSEA 0910-LP-115-1921, 2016. Chapters 20-21: Recompression therapy and recompression chamber operations. https://www.navsea.navy.mil/Portals/103/Documents/SUPSALV/Diving/US%20DIVING%20MANUAL_REV7.pdf
3. Divers Alert Network. Chapter 4: Treating Decompression Sickness. DAN Dive Medical Reference Books. https://dan.org/health-medicine/health-resource/dive-medical-reference-books/decompression-sickness/treating-dcs/
4. Longphre JM, Denoble PJ, Moon RE, Vann RD, Freiberger JJ. First aid normobaric oxygen for the treatment of recreational diving injuries. Undersea & Hyperbaric Medicine 2007;34(1):43-49. PMID: 17393938.
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9. Toklu AS, Cimsit M, Yildiz S, Uzun G, Korpinar S, Sezer H, Aktas S. Decompression sickness cases treated with recompression therapy between 1963 and 1998 in Turkey: review of 179 cases. Undersea & Hyperbaric Medicine 2014;41(3):217-221. PMID: 24984316.
10. Bonnington S, Banham N, Foley K, Gawthrope I. Oxygen toxicity seizures during United States Navy Treatment Table 6: an acceptable risk in monoplace chambers? Diving and Hyperbaric Medicine 2021;51(2):167-172. PMID: 34157732. DOI: 10.28920/dhm51.2.167-172.
11. Doolette DJ, Mitchell SJ. In-water recompression. Diving and Hyperbaric Medicine 2018;48(2):84-95. PMID: 29888380. DOI: 10.28920/dhm48.2.84-95.
12. Cooper JS, Hanson KC. Decompression Sickness. StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2025. https://www.ncbi.nlm.nih.gov/books/NBK537264/
13. Divers Alert Network. Project Dive Exploration (PDE). DAN Research. DCS incidence 3.4 per 10,000 dives. https://dan.org/research-reports/research-studies/project-dive-exploration-pde/
14. Huang ET, ed. UHMS Hyperbaric Medicine Indications Manual. 15th ed. North Palm Beach, FL: Best Publishing Company; 2023. Indication 5: Decompression sickness.
15. Centers for Medicare & Medicaid Services. National Coverage Determination 20.29: Hyperbaric Oxygen Therapy. Medicare NCD Manual Pub. 100-03, Ch. 1 Part 1. Version 4, effective 3 April 2017. Covered condition: decompression illness.