Hyperbaric oxygen therapy is the definitive treatment for arterial gas embolism. Recompression to 2.8 to 6.0 ATA shrinks intravascular gas bubbles, restores tissue perfusion, and accelerates nitrogen washout. Treatment must begin as soon as possible after diagnosis. Air or gas embolism is the first of the 14 conditions for which Health Canada-aligned hospital programmes provide HBOT under provincial health insurance.
Quick Answer
Does HBOT help air or gas embolism? Hyperbaric oxygen therapy is the definitive treatment for arterial gas embolism. Recompression to 2.8 to 6.0 ATA shrinks intravascular gas bubbles, restores tissue perfusion, and accelerates nitrogen washout. Treatment must begin as soon as possible after diagnosis. Air or gas embolism is the first of the 14 conditions for which Health Canada-aligned hospital programmes provide HBOT under provincial health insurance.
Air or gas embolism (AGE) is a life-threatening event in which gas enters the systemic arterial circulation and obstructs blood flow to end organs. The brain and spinal cord are the most common targets, producing stroke-like deficits, seizures, loss of consciousness, or sudden cardiovascular collapse. Coronary involvement can cause arrhythmia or arrest. Skin mottling, livedo reticularis, and visible retinal artery bubbles can occur. The presentation depends on bubble volume, distribution, and patient position at the moment of entry.
Iatrogenic causes are now the leading source of AGE in Canadian hospitals. Central venous catheter insertion or removal, mechanical ventilation with high inspiratory pressures, cardiopulmonary bypass, neurosurgery in the sitting position, hemodialysis line disconnection, percutaneous lung biopsy, endoscopy with insufflation, and laparoscopic surgery have all been documented as triggers. Pulmonary barotrauma from breath-hold ascent during scuba diving remains the classic non-iatrogenic cause and is the source most often seen by Vancouver General Hospital's hyperbaric unit, which serves divers along the Pacific coast.
Diagnosis is clinical. Sudden focal neurological deficit, cardiovascular collapse, or unexplained altered mental status appearing within minutes of any procedure that could introduce gas should prompt immediate suspicion. Imaging (CT, MRI, transthoracic echocardiography) may show intravascular gas but is never required before initiating treatment. Delays for confirmatory imaging are associated with worse outcomes.
HBOT addresses arterial gas embolism through three simultaneous mechanisms.
First, mechanical compression. Boyle's law dictates that bubble volume is inversely proportional to absolute pressure. At 2.8 ATA a bubble shrinks to roughly 36 percent of its surface volume; at 6.0 ATA it shrinks to about 17 percent. Smaller bubbles re-enter circulation, redistribute distally, and clear obstructed vessels.
Second, the oxygen window. Breathing 100 percent oxygen at depth raises arterial pO2 above 1,500 mmHg. The diffusion gradient from blood to bubble drives nitrogen out of the bubble far faster than under normobaric oxygen. Bubbles dissolve rather than persisting in tissue.
Third, tissue oxygenation downstream of the obstruction. Even when a bubble cannot be fully cleared, dissolved plasma oxygen (which at 3 ATA can supply tissue demand without any contribution from haemoglobin) keeps ischaemic tissue alive long enough for collateral perfusion to recover. This is why HBOT remains effective hours after bubbles themselves have resolved.
Typical Treatment Protocol
The standard protocol 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 decompression with intermittent air breaks to reduce oxygen toxicity risk. Total Table 6 duration is approximately 285 minutes (4 hours, 45 minutes). If neurological deficits are severe or do not improve at 2.8 ATA, treatment may be extended to Table 6A, which begins with an initial excursion to 6.0 ATA on a heliox or nitrox mixture before transitioning to oxygen at 2.8 ATA. Table 6A duration approaches 6 hours. Repeat treatments at 2.0 to 2.4 ATA on 100 percent oxygen, daily for two to seven sessions, may be given for residual deficits. The decision to continue is based on serial neurological 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 arterial gas embolism. No pharmacological alternative reverses intravascular gas obstruction.
Time to recompression is the strongest predictor of neurological outcome. Outcomes are best when treatment begins within 6 hours, but benefit has been documented at 24 hours and beyond, so transport should never be aborted on time grounds alone.
US Navy Treatment Table 6 produces complete or near-complete neurological recovery in 50 to 75 percent of treated AGE cases in published series, with higher recovery rates for shorter delays.
Iatrogenic AGE now outnumbers diving-related AGE in most Canadian academic hospitals. Central line placement, cardiac surgery, and neurosurgery in the sitting position are the most commonly identified procedural causes.
Repetitive HBOT sessions (2.0 to 2.4 ATA, daily) for residual deficits after initial recompression are supported by case series and have become standard at most North American hyperbaric units.
Air evacuation at altitude can worsen embolism through bubble re-expansion. Cabin pressurisation to sea-level equivalent or low-altitude rotor-wing transport is preferred.
Key supporting studies in the Canada Hyperbarics research database: PMID 41364856.
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.
World Neurosurg · 2025 · Systematic Review
Acta Anaesthesiol Scand · 2019 · Systematic Review
J Cardiothorac Surg · 2026 · Case Report
Air Med J · 2026 · Case Report
Medicine (Baltimore) · 2025 · Case Report
Suspected air or gas embolism is a code-stroke-equivalent emergency. The patient is recognised at the bedside (during or just after a procedure that could introduce gas, or after a diving event), placed supine, given 100 percent oxygen via non-rebreather mask, and kept normotensive while transfer to the nearest hyperbaric chamber is arranged. In Ontario, this is coordinated through CritiCall Ontario at 1-800-668-4357. The Divers Alert Network at 1-919-684-9111 is also available 24/7 for diving-related cases and provides hyperbaric-physician consultation and treatment-table selection.
The first chamber session begins as soon as the patient arrives at the receiving hospital, often within hours of the index event. Recompression to 2.8 ATA on 100 percent oxygen using US Navy Treatment Table 6 takes approximately 4 hours 45 minutes; the more intensive Table 6A used for severe deficits takes approximately 6 hours and starts with an excursion to 6.0 ATA on heliox or nitrox before transitioning to oxygen at 2.8 ATA. Multiplace chambers accommodate ventilator-dependent and infusion-dependent critical-care patients with full monitoring inside the chamber.
After the initial recompression, repeat sessions at 2.0 to 2.4 ATA on 100 percent oxygen, once daily, are delivered for residual neurological deficits. The number of follow-on sessions is decided by serial neurological examination, with most patients receiving two to seven additional sessions. Recovery from arterial gas embolism is typically rapid for the bubble-related component but can be prolonged for any residual ischaemic injury; rehabilitation needs are addressed during and after the acute course. Time to first recompression is the strongest single determinant of outcome.
Air or gas embolism is recognised by Health Canada as one of the 14 conditions for which hyperbaric oxygen is the established standard of care. All 11 hospital-based hyperbaric programmes in Canada (seven provinces: Ontario, Quebec, British Columbia, Alberta, Nova Scotia, Newfoundland, and Saskatchewan) treat AGE as a 24/7 emergency indication under provincial health insurance: OHIP in Ontario, RAMQ in Quebec, MSP in British Columbia, AHCIP in Alberta, MSI in Nova Scotia, MCP in Newfoundland, and Saskatchewan Health.
For patients in the six provinces and territories without an in-province hospital programme (Manitoba, New Brunswick, Prince Edward Island, Yukon, Northwest Territories, Nunavut), emergency AGE treatment is coordinated through the nearest hospital programme. CritiCall Ontario (1-800-668-4357) is the standard inter-facility transfer line for Ontario referrals and is widely used as the first call for diving and iatrogenic embolism cases requiring chamber access. The Divers Alert Network (DAN) emergency line, 1-919-684-9111, is staffed 24/7 by hyperbaric physicians and is the international reference for diving-related AGE consultation.
Ground or rotor-wing transport at low altitude (below 300 metres above the embolism site, when possible) 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 Air or Gas Embolism, 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 Air or Gas Embolism, 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 AGE because the condition is rapidly fatal without recompression. The single condition that must be addressed before chamber entry is untreated pneumothorax, which will tension under compression and again under 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 and mortality of untreated embolism, and treatment generally proceeds. Pregnancy is not a contraindication.
Yes. Arterial gas embolism is a medical emergency requiring immediate recompression. Symptoms can progress from focal neurological deficit to cardiovascular collapse within minutes. Delays measured in hours are associated with worse outcomes.
As soon as physically possible. Outcomes are best when treatment begins within 6 hours, but benefit has been demonstrated at 24 hours and longer. Time should not be used as a reason to withhold treatment.
Yes. Air or gas embolism is recognised by Health Canada and covered as an emergency indication at all 11 hospital-based hyperbaric programmes in Canada under OHIP, RAMQ, MSP, AHCIP, MSI, MCP, and Saskatchewan Health.
Table 6 is the standard recompression protocol for arterial gas embolism and serious decompression sickness. It begins with recompression to 2.8 ATA (60 feet of seawater) on 100 percent oxygen for 75 minutes, followed by a controlled stepwise decompression with intermittent air breaks to manage oxygen toxicity. Total duration is roughly 285 minutes.
The leading iatrogenic causes are central venous catheter insertion or removal, mechanical ventilation with high airway pressures, cardiopulmonary bypass, neurosurgery in the sitting position, hemodialysis line disconnection, percutaneous lung biopsy, and laparoscopic insufflation. Diving barotrauma is the leading non-iatrogenic cause.
No. The diagnosis is clinical. Imaging (CT, MRI, transthoracic echocardiography) may show intravascular gas, but waiting for confirmatory imaging delays treatment and worsens outcomes. Suspected AGE based on history and presentation is sufficient justification for emergency recompression.
Air transport is possible but not preferred. Reduced ambient pressure at altitude re-expands residual bubbles and can worsen the embolism. If rotor-wing transport is required it should be flown as low as terrain allows, ideally under 300 metres above the embolism site. Fixed-wing transport requires cabin pressurisation to sea-level equivalent.
The DAN emergency line, 1-919-684-9111, is staffed 24/7 by hyperbaric physicians and is widely used by Canadian emergency departments for consultation on diving-related embolism, treatment-table selection, and chamber referral. It complements rather than replaces provincial transfer lines such as CritiCall Ontario (1-800-668-4357).
The standard HBOT course for air or gas embolism is 1 to 5 sessions at a treatment pressure of 2.8 to 3.0 ATA, with each session lasting 90 to 120 minutes door-to-door. Emergency indications use front-loaded protocols (often two to three sessions in the first 24 hours), while chronic indications follow daily or near-daily scheduling Monday to Friday over several weeks. The exact protocol is set by the receiving hospital's hyperbaric physician based on clinical response and tolerability; courses can be extended or shortened in response to interim assessment.
In Canada, air or gas embolism is one of the 14 Health Canada-recognised conditions for HBOT, so treatment at hospital-based programmes is covered by provincial health insurance (OHIP, MSP, AHCIP, RAMQ, MSI, Saskatchewan Health, MCP) with a physician referral, at no out-of-pocket cost. The only absolute contraindication to HBOT is untreated pneumothorax (trapped intrathoracic air expands on decompression); concurrent bleomycin chemotherapy (oxygen-induced pulmonary fibrosis risk) and concurrent disulfiram (interferes with superoxide dismutase, the enzyme that neutralises hyperbaric-oxygen-generated free radicals) are treated as effectively absolute at most programmes, though the UHMS classifies them as relative contraindications. Relative contraindications include severe haemodynamic instability requiring continuous high-dose vasopressor titration, uncontrolled seizure disorder, severe COPD with bullous lung disease, and uncontrolled claustrophobia. Pregnancy is not a contraindication.
Related conditions: Central Retinal Artery Occlusion