Hyperbaric oxygen therapy is the definitive treatment for decompression sickness, also called the bends or caisson disease. Recompression shrinks intravascular and intra-tissue nitrogen bubbles by Boyle's law, restores tissue perfusion, and accelerates nitrogen washout from supersaturated tissues. Emergency treatment uses standardised US Navy Treatment Tables (Table 6 most commonly, Table 6A for severe neurological cases). Decompression sickness is recognised by Health Canada as one of the 14 conditions for which provincial health insurance covers HBOT at hospital-based programmes.
Quick Answer
Does HBOT help decompression sickness? Hyperbaric oxygen therapy is the definitive treatment for decompression sickness, also called the bends or caisson disease. Recompression shrinks intravascular and intra-tissue nitrogen bubbles by Boyle's law, restores tissue perfusion, and accelerates nitrogen washout from supersaturated tissues. Emergency treatment uses standardised US Navy Treatment Tables (Table 6 most commonly, Table 6A for severe neurological cases). Decompression sickness is recognised by Health Canada as one of the 14 conditions for which provincial health insurance covers HBOT at hospital-based programmes.
Decompression sickness (DCS), commonly known as "the bends," occurs when dissolved inert gas (most often nitrogen, sometimes helium in mixed-gas diving) comes out of solution and forms bubbles in blood and tissues during rapid reduction of ambient pressure. The classic setting is ascent from depth in scuba or commercial diving, but DCS can also occur in compressed-air tunnel and caisson workers, aviators experiencing sudden cabin depressurisation, astronauts during extra-vehicular activity, and submariners performing emergency ascent. The condition has been recognised since the construction of the Brooklyn Bridge in the 1870s, where it was called caisson disease and was responsible for hundreds of deaths and disabling injuries among the workers.
DCS is traditionally classified as Type I (joint pain, skin marbling, lymphatic involvement, generally considered milder) and Type II (neurological involvement of the spinal cord, brain, inner ear, or cardiopulmonary system, with potential for permanent disability or death). The 1990 Divers Alert Network reclassification simplified the practical scheme to "decompression illness" (DCI), encompassing both DCS and arterial gas embolism, recognising that the two conditions overlap clinically and respond to the same recompression treatment. The Canadian recreational diving community follows the DAN scheme operationally, with the older Type I/II designation still used for descriptive and reporting purposes.
Symptoms typically appear within minutes to several hours after surfacing. Joint pain (most often shoulder or elbow, characteristically deep, dull, and unrelieved by position change) is the most common presentation. Spinal cord DCS produces back pain, paraesthesia, weakness, and (in severe cases) paraplegia. Inner-ear DCS produces vertigo, nausea, and tinnitus. Cerebral DCS produces stroke-like deficits. Pulmonary DCS ("the chokes") produces substernal pain, cough, and dyspnea and is a respiratory emergency. Skin DCS ("the niggles" or cutis marmorata) produces a characteristic mottled marbling, often associated with lymphatic obstruction. Untreated DCS can resolve, persist, or progress to permanent disability or death.
Canadian DCS cases are concentrated along the Pacific coast (recreational and commercial diving served by Vancouver General Hospital), the Atlantic coast and offshore oil sector (served by the Health Sciences Centre in St. John's, Newfoundland, and the Halifax Infirmary), and the Great Lakes recreational diving community (served by Hamilton General Hospital and Toronto General Hospital).
Hyperbaric oxygen therapy treats decompression sickness through three convergent mechanisms.
First, mechanical recompression. Boyle's law dictates that bubble volume is inversely proportional to absolute pressure. At 2.8 ATA (the standard recompression depth on US Navy Treatment Table 6), a bubble shrinks to approximately 36 percent of its surface volume. At 6.0 ATA (used on Table 6A for severe neurological cases), it shrinks to about 17 percent. Smaller bubbles re-enter circulation, redistribute distally to less-critical tissue beds, and clear obstructed vessels. The mechanical recompression effect is the foundation of the treatment.
Second, accelerated nitrogen washout via the oxygen window. Breathing 100 percent oxygen at hyperbaric pressure raises arterial pO2 above 1,500 mmHg, creating an enormous diffusion gradient that drives nitrogen out of the bubble into surrounding plasma far faster than would occur on normobaric oxygen or air. The bubble dissolves rather than persisting in tissue. The oxygen-window effect is what differentiates modern oxygen-based recompression from the historical air-only recompression tables, which were less effective and exposed divers to additional decompression obligation.
Third, restoration of tissue oxygenation downstream of bubble obstruction. Even when bubbles cannot be fully cleared, dissolved plasma oxygen at hyperbaric pressure can supply tissue oxygen demand without any contribution from hemoglobin in the affected vascular bed. This keeps ischemic tissue alive long enough for collateral perfusion to recover, and explains why HBOT remains effective hours and even days after the original bubble injury, when bubbles themselves have largely dissolved.
Typical Treatment Protocol
The standard protocol for symptomatic decompression sickness is US Navy Treatment Table 6, beginning with recompression to 2.8 ATA (60 feet of seawater equivalent) on 100 percent oxygen for 75 minutes, followed by a controlled stepwise decompression with intermittent air-breaks to limit oxygen toxicity risk. Total Table 6 duration is approximately 285 minutes (4 hours, 45 minutes). For severe Type II (neurological) cases, particularly those with spinal cord involvement, treatment is extended to Table 6A, which begins with an initial excursion to 6.0 ATA on heliox or nitrox before transitioning to oxygen at 2.8 ATA. Table 6A duration approaches 6 hours. Mild Type I cases without progression may be treated on Table 5 (2.8 ATA, 135 minutes total), but most contemporary Canadian programmes use Table 6 for all symptomatic DCS to err on the side of more complete recompression. After the initial recompression, repeat sessions at 2.0 to 2.4 ATA on 100 percent oxygen are delivered once or twice daily for residual symptoms, with the number of follow-on sessions guided by serial neurological and clinical examination rather than fixed schedules. While awaiting transport to a chamber, the patient should be kept supine, given 100 percent oxygen by tight-fitting non-rebreather mask, kept normotensive with isotonic fluids, and have any pneumothorax decompressed.
Level A - Strong Evidence
Supported by high-quality RCTs and systematic reviews
HBOT is the only definitive treatment for decompression sickness. No pharmacological alternative reverses the underlying nitrogen-bubble pathophysiology.
US Navy Treatment Table 6 has been the standard of care since the 1960s, with continuous refinement based on clinical experience accumulated across thousands of cases. Table 6 is in use at every Canadian hospital hyperbaric programme.
Time to recompression is the strongest single predictor of neurological outcome. Outcomes are best when treatment begins within 6 hours, but benefit has been documented at 24 hours and beyond, and treatment is offered at any interval up to two weeks after the dive event for residual symptoms.
Complete resolution of symptoms occurs in the majority of mild Type I cases when treatment is initiated promptly. Severe Type II cases (spinal cord DCS, cerebral DCS, vestibular DCS) have higher rates of residual deficit but still benefit substantially from prompt and adequate recompression.
Air evacuation at altitude can worsen DCS through bubble re-expansion. Cabin pressurisation to sea-level equivalent or low-altitude rotor-wing transport is preferred. The classic teaching is \"avoid air travel after diving for 24 hours; avoid air travel after DCS until cleared by a hyperbaric physician.\"
The Divers Alert Network at 1-919-684-9111 is the international 24/7 consultation line for diving-related DCS and is widely used by Canadian emergency departments for treatment-table guidance and chamber referral.
Highest-evidence-tier studies tagged to this condition in the Canada Hyperbarics research database, ranked by evidence tier (1 = meta-analysis or RCT, 2 = cohort, 3 = case series), most recent first.
Undersea Hyperb Med · 2019 · Clinical Guideline
Diving Hyperb Med · 2017 · RCT
Undersea Hyperb Med · 2014 · Review
Undersea Hyperb Med · 2013 · Systematic Review
Suspected decompression sickness is a hyperbaric emergency. Recreational and commercial divers in Canada are typically familiar with the symptoms and are encouraged to call the Divers Alert Network (DAN) at 1-919-684-9111 from anywhere in the world; DAN is staffed 24/7 by hyperbaric physicians and provides immediate consultation, treatment-table selection, and guidance on the nearest accepting chamber. The local emergency department or marine rescue is also notified.
While awaiting transport, the patient is kept supine on 100 percent oxygen by non-rebreather mask, given oral or IV fluids, and protected from further altitude exposure. Air evacuation, when needed, should be at the lowest practical altitude (below 300 metres above the dive site if possible) with cabin pressurisation to sea-level equivalent for fixed-wing transport. The Canadian Coast Guard, civilian helicopter services, and provincial air-ambulance systems coordinate transport from offshore and remote dive sites.
The first hyperbaric session begins as soon as the patient arrives at the receiving hospital, usually within hours of the dive incident in coastal cases and within 12 to 24 hours for inland or remote dives. US Navy Treatment Table 6 takes approximately 4 hours 45 minutes; Table 6A used for severe neurological cases takes approximately 6 hours. Multiplace chambers accommodate the long treatment durations and the critical-care needs of the most severe cases. After the initial recompression, repeat sessions at 2.0 to 2.4 ATA on 100 percent oxygen, once or twice daily, are delivered for residual symptoms. Total treatment course depends on severity and response, ranging from a single Table 6 in mild cases to two to seven additional sessions in severe cases. Recovery is typically rapid for the bubble-related component but can be prolonged for any residual neurological injury.
Decompression sickness is recognised by Health Canada as one of the 14 conditions for which hyperbaric oxygen is the definitive treatment. All 11 hospital-based hyperbaric programmes in Canada accept DCS as an emergency indication under provincial health insurance: OHIP in Ontario, MSP in British Columbia, AHCIP in Alberta, RAMQ in Quebec, MSI in Nova Scotia, MCP in Newfoundland and Labrador, and Saskatchewan Health.
The key Canadian facilities for DCS by geography are: Vancouver General Hospital's Leon Judah Blackmore Pavilion (the principal Pacific-coast chamber, serving recreational divers along the BC coast and commercial divers on the offshore fishery and aquaculture sector); the Health Sciences Centre in St. John's, Newfoundland (the principal Atlantic-coast chamber, serving recreational divers and the offshore oil and gas sector); the Halifax Infirmary (Atlantic-coast secondary referral); the three Ontario hospital programmes including Hamilton General Hospital and Toronto General Hospital (Great Lakes recreational diving); and the Quebec hospital programmes for Lawrentian and Saguenay-area recreational diving.
The Divers Alert Network at 1-919-684-9111 is the standard 24/7 consultation line for diving-related DCS. DAN provides physician-to-physician triage, treatment-table guidance, and chamber-locator services. Canadian commercial divers typically carry DAN membership and are familiar with the DAN protocol. CritiCall Ontario at 1-800-668-4357 is the standard inter-facility transfer line for Ontario referrals and is widely used for diving cases requiring chamber access.
Ground or rotor-wing transport at low altitude is preferred over fixed-wing transport because reduced ambient pressure at altitude expands residual bubbles. If air transport is unavoidable, cabin pressurisation to sea-level equivalent should be requested.
Hyperbaric oxygen therapy for the 14 Health Canada-recognised conditions, including Decompression Sickness, is delivered at the 11 hospital hyperbaric programmes located in seven provinces (Ontario, Quebec, British Columbia, Alberta, Nova Scotia, Newfoundland and Labrador, and Saskatchewan). The six provinces and territories without an in-province hospital programme (Manitoba, New Brunswick, Prince Edward Island, Yukon, Northwest Territories, and Nunavut) route patients to the nearest receiving hospital programme. Use the links below for province-specific coverage, referral pathway, and emergency routing details.
Hospital + Private
OHIP (Ontario Health Insurance Plan)
Hospital Only
MSP (Medical Services Plan)
Hospital + Private
Alberta Health / AHCIP
Hospital Only
RAMQ
Disrupted
Saskatchewan Health Authority
No Hospital Chamber
Manitoba Health
Hospital Only
MSI (Medical Services Insurance)
No Hospital Chamber
Medicare NB
Hospital Only
MCP (Medical Care Plan)
Out-of-Province Referral
Health PEI
Out-of-Province Referral
Yukon Health and Social Services
Out-of-Province Referral
NWT Health and Social Services
Out-of-Province Referral
Nunavut Department of Health
For acute or emergency presentations of Decompression Sickness, call 911 first. The receiving emergency department coordinates urgent transfer to the nearest hospital hyperbaric programme through the relevant provincial transfer network (CritiCall Ontario at 1-800-668-4357, BC Patient Transfer Network, EHS Nova Scotia, or equivalent). For diving-related emergencies, the Divers Alert Network (DAN) emergency hotline is 1-919-684-9111.
There are no absolute contraindications to HBOT in suspected decompression sickness because the condition can progress to permanent disability or death without recompression. The single condition that must be addressed before chamber entry is untreated pneumothorax, which will tension under compression and decompression; emergency tube thoracostomy is performed first. Relative contraindications including severe chronic obstructive pulmonary disease with bullous disease, recent thoracic or middle-ear surgery, claustrophobia, and uncontrolled seizure disorder are weighed against the certain morbidity of untreated DCS, and treatment generally proceeds. Pregnancy is not a contraindication. For patients with a history of cardiac decompensation, the cardiologic team is consulted because the increase in plasma oxygen content during HBOT can transiently increase left-ventricular afterload. This rarely changes the decision to recompress.
Administer 100% oxygen, keep the patient horizontal, hydrate with oral fluids if conscious, and call DAN (Divers Alert Network) at 919-684-9111 for emergency consultation. Transport to the nearest hyperbaric facility immediately.
The initial treatment using US Navy Treatment Table 6 takes approximately 4 hours and 45 minutes, with possible extensions. Additional daily treatments may be needed for 2-5 days depending on severity and response.
Yes. DCS is an emergency indication covered at all hospital-based HBOT facilities across Canada under provincial health insurance plans.