Physician Referral Guide: Hyperbaric Oxygen for Decompression Sickness

Assessing the patient before referral

While arranging recompression, the receiving emergency department should:

• Place the patient supine and start 100 percent oxygen by a tight-fitting non-rebreather mask immediately, continuing it through transport. Surface oxygen accelerates inert-gas washout and can improve symptoms before chamber entry.
• Keep the patient normotensive with isotonic intravenous fluids; divers are frequently dehydrated and hypovolaemia worsens tissue perfusion.
• Perform and document a focused neurological examination (motor, sensory, cerebellar, cranial-nerve, and bladder function) to establish a baseline against which response to recompression can be tracked.
• Exclude or treat pneumothorax before any thought of chamber entry; a chest radiograph or point-of-care ultrasound is appropriate where the history or examination raises concern.
• Record a detailed dive history: depth and bottom time, gas mix (air, nitrox, or heliox), number and profile of dives, rate of ascent, any missed decompression stops, the surface interval, and the time of symptom onset relative to surfacing.

Do not delay referral to complete imaging or laboratory work. Recompression is the intervention that changes outcome, and adjunctive investigations should not hold up the call to the chamber.

What the evidence supports

Hyperbaric oxygen, delivered as recompression, is the only definitive treatment for decompression sickness. No pharmacological alternative reverses the underlying nitrogen-bubble pathophysiology. The condition page rates the evidence base as strong, supported by high-quality studies and systematic reviews, and grounded in a coherent and well-established mechanism.

The mechanistic rationale is threefold and convergent. First, mechanical recompression: bubble volume is inversely proportional to absolute pressure, so at the standard treatment depth of 2.8 ATA a bubble shrinks to roughly 36 percent of its surface volume, and at 6.0 ATA to about 17 percent. Second, accelerated nitrogen washout: breathing 100 percent oxygen at pressure raises arterial pO2 above 1,500 mmHg, creating a steep diffusion gradient that drives inert gas out of bubbles and tissues. Third, restoration of tissue oxygenation: oxygen dissolved in plasma can supply tissue downstream of bubble obstruction while perfusion is re-established.

The strongest predictor of neurological outcome is time to recompression. Outcomes are best when treatment begins within 6 hours of symptom onset, but benefit has been documented at 24 hours and beyond, and recompression is offered at any interval up to two weeks after the dive for residual symptoms. Complete resolution occurs in the majority of mild Type I cases treated promptly. Severe Type II cases (spinal cord, cerebral, and vestibular decompression sickness) have higher rates of residual deficit but still benefit substantially from prompt, adequate recompression. Because the condition can progress to permanent disability or death without treatment, recompression is offered even at long intervals and even when the diagnosis is uncertain.

The Canadian referral pathway

Decompression sickness is accepted as an emergency indication at all 11 Canadian hospital-based hyperbaric programmes and is covered by every provincial plan without prior authorisation. You can read the full clinical background on the Canada Hyperbarics decompression sickness page.

• First call for any suspected case: the Divers Alert Network (DAN) 24/7 emergency line at 1-919-684-9111, staffed by hyperbaric physicians, provides immediate consultation, treatment-table guidance, and direction to the nearest accepting chamber.
• Pacific coast: Vancouver General Hospital (Leon Judah Blackmore Pavilion) is the principal Pacific-coast chamber, serving recreational divers along the BC coast and the commercial offshore and aquaculture sectors; covered under MSP.
• Atlantic coast: Health Sciences Centre in St. John's is the principal Atlantic-coast chamber, serving recreational divers and the offshore oil and gas sector, with the Halifax Infirmary as a secondary referral centre; covered under MCP (Newfoundland and Labrador) and MSI (Nova Scotia).
• Great Lakes: Toronto General Hospital (UHN) and Hamilton General Hospital serve Great Lakes recreational diving. In Ontario, CritiCall Ontario at 1-800-668-4357 is the standard inter-facility transfer line and arranges transport when needed.
• Inland and regions without a hospital programme: route via DAN and the nearest provincial coordination line to the closest accepting programme, with air-ambulance transfer where required.

Air evacuation at altitude can worsen decompression sickness through bubble re-expansion. Where air transport is unavoidable, cabin pressurisation to a sea-level equivalent, or low-altitude rotor-wing transport, is preferred.

How to use the research list below

The list contains every decompression sickness study in the Canada Hyperbarics database that was published in 2020 or later and has a freely available full-text version, each linked directly to that full text. Paywalled and abstract-only studies are excluded, and retracted studies are removed. This is a reference list, not a set of summaries. Counts and the open-access set refresh each quarter.