Physician Referral Guide: Hyperbaric Oxygen for Air or Gas Embolism

Assessing the patient before referral

While arranging recompression, the receiving department should stabilise the patient and begin treatment without delay:

• Keep the patient supine. Avoid head-up positioning, and do not delay transfer to position the patient.
• Place the patient on 100 percent oxygen by tight-fitting non-rebreather mask immediately and continue it through transport. High-flow oxygen begins shrinking the gas bubbles and establishing the oxygen gradient before chamber entry.
• Maintain normotension with isotonic fluids; hypotension worsens cerebral and spinal perfusion in already-ischaemic tissue.
• Decompress any pneumothorax with a chest tube before chamber entry. An untreated pneumothorax is the one absolute barrier to recompression and must be addressed first.
• Document a baseline neurological examination. Serial neurological assessment guides both the chamber protocol and the decision on follow-up sessions, so an accurate reference point at presentation is essential.
• Record the exposure history: the procedure or dive involved, the time of symptom onset, and the interval since the suspected embolic event, since time to recompression is the factor that most directly predicts outcome.

A note on transport: air evacuation at altitude can worsen the embolism through bubble re-expansion. Cabin pressurisation to a sea-level equivalent or low-altitude rotor-wing transport is preferred when air transfer is unavoidable.

What the evidence supports

Recompression for arterial gas embolism is the established standard of care and is recognised as an accepted HBOT indication within Health Canada-aligned hospital practice. Because the condition cannot ethically be randomised, the supporting evidence comes from physiological rationale and consistent clinical experience rather than controlled trials. In published case series, the standard US Navy Treatment Table 6 has been associated with complete or near-complete neurological recovery in roughly 50 to 75 percent of treated cases, with the best results reported when treatment begins early.

The mechanistic rationale is well established and operates through three simultaneous effects. First, mechanical compression: under Boyle's Law a bubble shrinks to roughly 36 percent of its original (surface) volume at 2.8 ATA and to about 17 percent at 6.0 ATA, directly relieving vascular obstruction. Second, the oxygen window: breathing 100 percent oxygen at depth raises arterial pO2 above 1,500 mmHg, steepening the gradient that drives nitrogen out of the trapped bubbles. Third, tissue oxygenation: the oxygen dissolved in plasma at depth can help sustain tissue demand with little reliance on haemoglobin, helping to keep ischaemic brain and spinal cord viable while the bubble resolves.

The most consistent and important predictor of recovery is time to recompression. Outcomes are best when treatment begins within about 6 hours, but meaningful benefit has been documented at 24 hours and beyond, so delayed presentation is not a reason to withhold referral.

The Canadian referral pathway

Air or gas embolism is treated as an emergency at Canadian hospital-based hyperbaric programmes and is covered by provincial health insurance. Eleven hospital programmes operate across seven provinces (Ontario, Quebec, British Columbia, Alberta, Nova Scotia, Newfoundland and Labrador, and Saskatchewan), with coverage under OHIP, RAMQ, MSP, AHCIP, MSI, MCP, and Saskatchewan Health respectively.

• Ontario: call CritiCall Ontario at 1-800-668-4357, the provincial line that connects emergency departments to accepting hospital programmes and helps arrange transport when needed. CritiCall can also be a useful first call for general inter-facility coordination.
• British Columbia: route to the hospital hyperbaric programme in Vancouver; covered under MSP.
• Alberta: route to a hospital hyperbaric programme in Edmonton or Calgary; covered by AHCIP.
• Quebec: RAMQ covers the Montreal-area and Levis hospital hyperbaric programmes.
• Atlantic Canada: Nova Scotia (MSI) and Newfoundland and Labrador (MCP) operate hospital programmes; Saskatchewan Health covers the Saskatchewan programme.
• Provinces and territories without a chamber: arrange inter-provincial air or ground transfer to the nearest accepting hospital programme, with attention to cabin pressurisation if air transport is used.

For diving-related cases, the Divers Alert Network 24/7 emergency line at 1-919-684-9111 is staffed by hyperbaric physicians and can help Canadian emergency departments locate the nearest accepting chamber and advise on transport.

How to use the research list below

The list contains every air or gas embolism 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.

You can review the broader clinical overview, including the full taxonomy of iatrogenic and diving-related sources, on the air or gas embolism condition page.