TL;DR: Before referring a patient for hyperbaric oxygen therapy (HBOT), Canadian physicians should document the indication, rule out untreated pneumothorax, confirm tympanic membrane mobility, review medications for HBOT-sensitive drugs, and optimize cardiac and glycaemic status. A structured pre-HBOT workup reduces treatment interruption, prevents avoidable adverse events, and speeds up intake at the receiving centre. This guide outlines the ten-step screening process recommended for Canadian referring physicians in 2026.
A pre-HBOT workup is a structured set of clinical assessments completed before a patient begins hyperbaric oxygen therapy. The goal is to confirm the indication, screen for conditions that would compromise safety under pressure, and document baseline status so the treating team can recognize complications early. For Canadian referring physicians, a clean workup accelerates intake at hospitals and regulated facilities and protects patients from avoidable adverse events such as middle ear barotrauma, pulmonary complications, and unmasked heart failure.
Canada Hyperbarics publishes this checklist for family physicians, specialists, and nurse practitioners who are preparing a referral to a regulated hyperbaric facility. The recommendations draw on current PubMed evidence and align with Undersea and Hyperbaric Medical Society and Canadian Undersea and Hyperbaric Medical Association guidance. This is general clinical information, not a substitute for the specific screening protocols at the receiving centre.
Why does pre-referral screening matter for HBOT?
HBOT is generally safe when patients are selected carefully, but pressurization to 2.0 to 2.4 atmospheres absolute introduces physiological stresses that routine outpatient care does not. Trapped gas in the lung or middle ear can expand, cardiac preload and afterload shift during compression and decompression, and some medications interact adversely with high partial pressures of oxygen.
A five-year retrospective analysis of 2,610 patients at a French hyperbaric centre found middle ear barotrauma in 10.04% of patients, with older age, female sex, prior head and neck radiotherapy, smoking, and obstructive breathing disorders identified as risk factors. Barotrauma was a leading cause of premature discontinuation of therapy. Early identification of risk factors at the referral stage reduces dropouts and interruptions in the treatment course.
What information belongs in the referral document?
Every HBOT referral in Canada should include the following elements. A complete package reduces back-and-forth between the referring physician and the receiving centre and speeds up the first appointment.
- Patient demographics and contact information including provincial health card number.
- Specific indication using the UHMS or CUHMA-recognized term (for example, delayed radiation injury, soft tissue, pelvic rather than a general diagnosis).
- Brief clinical history focused on the indication, prior treatments tried, and response.
- Relevant imaging and investigations including chest imaging, audiometry if ear history is concerning, and condition-specific studies such as MRI for radiation injury.
- Current medications with a flag on any drugs known to interact with hyperbaric oxygen.
- Comorbidities with particular attention to cardiac, pulmonary, and ear, nose and throat (ENT) history.
- Functional status and mobility since patients must be able to enter and tolerate the chamber.
- Goals of treatment and the outcome measure the referring physician wants tracked.
Which pulmonary assessments should be completed first?
Untreated pneumothorax is the single absolute contraindication to elective HBOT. Trapped intrapleural gas expands as the chamber decompresses, which can convert a small pneumothorax into a tension pneumothorax. Any patient with a history of spontaneous pneumothorax, thoracic surgery, penetrating chest trauma, or advanced bullous lung disease should have a recent chest x-ray or computed tomography before the first session.
- Obtain a posterior-anterior chest x-ray within 30 days of the expected start date.
- Order a thoracic CT scan if the patient has a history of bullous emphysema, prior pneumothorax, or lung resection.
- Consider pulmonary function testing for patients with chronic obstructive pulmonary disease (COPD) to quantify air trapping and bullae risk.
- Document smoking status and counsel on cessation before treatment where possible.
How should cardiac status be optimized before HBOT?
A retrospective cohort study from Toronto General Hospital and Rouge Valley Hyperbaric Medical Centre reviewed 23 patients with pre-existing heart failure who underwent elective HBOT. Twenty-one patients completed treatment without complications. Two patients developed HBOT-related heart failure exacerbations, including one with heart failure with preserved ejection fraction (HFpEF), suggesting the old practice of excluding only patients with reduced ejection fraction is too narrow.
Practical implications for referring physicians in Canada:
- Document left ventricular ejection fraction (LVEF) within the last year for any patient with known cardiac disease, or obtain a recent transthoracic echocardiogram if unclear.
- Optimize fluid balance before referral. Ensure the patient is compliant with diuretics and not in a decompensated state.
- Review ischaemic risk. Patients with recent acute coronary syndrome, uncontrolled angina, or recent cardiac surgery need cardiology clearance.
- Include a recent electrocardiogram (ECG) in the referral package when cardiac disease is present.
- Flag implanted cardiac devices such as pacemakers and implantable cardioverter-defibrillators (ICDs). The device manufacturer must confirm pressure tolerance before HBOT.
What ear, nose, and throat screening is required?
Middle ear barotrauma is the most common adverse event in hyperbaric practice. Prevention starts at the referral stage. The large French cohort cited above showed that altered tympanic mobility on initial examination was a strong predictor of barotrauma during treatment.
- Examine the tympanic membranes for mobility, perforation, effusion, and scarring. Refer to ENT if mobility is abnormal.
- Ask about equalization ability. Patients who cannot clear their ears while flying or diving will likely need pre-treatment myringotomy or tympanostomy tubes.
- Document prior head and neck radiotherapy, which is a significant risk factor for barotrauma and may reduce eustachian tube function.
- Treat active sinusitis or allergic rhinitis before referral. Topical intranasal corticosteroids may be appropriate for patients with chronic rhinitis.
- Avoid relying on pseudoephedrine prophylaxis alone. A 2025 randomized controlled trial found no benefit over placebo for barotrauma prevention in first-session HBOT patients.
Which medications need review before a patient starts HBOT?
Several commonly prescribed drugs interact with hyperbaric oxygen and should be flagged in the referral. The receiving centre will make final decisions, but early identification prevents last-minute delays.
| Medication or class | Concern | Typical action |
|---|---|---|
| Bleomycin (current or recent) | Pulmonary fibrosis risk with high-dose oxygen | Consult hyperbaric physician; timing often decisive |
| Doxorubicin | Cardiotoxicity potentiation | Coordinate with oncology |
| Disulfiram | Blocks superoxide dismutase, theoretical oxygen toxicity risk | Discontinue before HBOT in most cases |
| Cisplatin | Impaired wound healing when combined with HBOT | Timing coordination with oncology |
| Insulin and sulfonylureas | HBOT lowers blood glucose | Pre-session glucose check, dose adjustment |
| Topical petroleum products on day of session | Fire hazard in oxygen-rich environment | Avoid on treatment days |
How should glycaemic control be managed before hyperbaric sessions?
Hyperbaric oxygen lowers capillary blood glucose by roughly 2 to 3 mmol/L during a standard session. Patients with insulin-dependent diabetes and those on sulfonylureas are at risk of intra-chamber hypoglycaemia. Referring physicians can help by providing a current HbA1c and noting whether the patient monitors capillary glucose reliably.
- Include a recent HbA1c (within three months) in the referral document.
- Advise patients not to skip meals before sessions and to carry glucose tablets or juice.
- Flag patients with a history of hypoglycaemia unawareness for close intra-chamber monitoring.
- Consider a medication review with the diabetes educator if daytime glycaemic control is unstable.
What psychological and cognitive factors should be documented?
A typical treatment course involves 20 to 40 sessions in a sealed chamber. Patients with uncontrolled claustrophobia, severe anxiety, or cognitive impairment may struggle with tolerance. Monoplace chambers are a single-person environment; multiplace chambers accommodate multiple patients and a chamber attendant, which some patients find reassuring.
- Ask directly about claustrophobia and prior tolerance of MRI or enclosed spaces.
- Document any history of panic disorder, post-traumatic stress disorder (PTSD), or cognitive impairment that might interfere with session cooperation.
- Arrange a pre-treatment tour of the facility for anxious patients where possible.
- Note that some centres allow short-term anxiolytic premedication; this is a shared decision with the hyperbaric physician.
Which absolute and relative contraindications should you rule out?
The list below summarizes current Canadian hyperbaric practice. The only true absolute contraindication to elective HBOT is untreated pneumothorax. All others are relative and are weighed case-by-case at the receiving centre.
| Category | Examples | Status |
|---|---|---|
| Absolute | Untreated pneumothorax | Defer until resolved |
| Relative (strong) | Current bleomycin, severe COPD with bullae, decompensated heart failure, uncontrolled seizure disorder, hyperthermia | Case-by-case, often requires optimization first |
| Relative (moderate) | Active upper respiratory infection, middle ear disease, pregnancy (except carbon monoxide poisoning), claustrophobia, implanted devices | Manage and proceed or defer briefly |
| Special populations | Pacemakers, ICDs, insulin pumps, cochlear implants | Confirm device pressure rating with manufacturer |
A 2025 scoping review in Diving and Hyperbaric Medicine examined defibrillation during HBOT and confirmed that defibrillation is strictly contraindicated inside monoplace chambers due to fire risk in the oxygen-enriched environment. Patients at high arrhythmia risk should be flagged so the hyperbaric centre can choose the appropriate chamber type.
How does coverage and authorization fit into the workup?
In Canada, HBOT is publicly funded for approved indications when delivered at a hospital-based hyperbaric unit. Private facilities also offer HBOT for indications not publicly covered, often at patient expense or through extended health benefits. The referring physician can expedite access by:
- Confirming whether the indication is a publicly funded indication in the patient’s province.
- Identifying the closest hospital-based centre or regulated private facility through the Canada Hyperbarics directory of hospitals and regulated facilities.
- Completing the receiving centre’s intake form in addition to the clinical referral.
- Providing the patient with a cost estimate and any prior authorization letters needed for private insurance.
Review the relevant provincial coverage information for the patient’s home province before finalizing the referral. Approved indications and reimbursement rules vary by province.
What is the ten-step pre-HBOT workup checklist?
Use this sequence for every referral. It covers the safety essentials in the order most likely to uncover blockers early.
- Confirm the indication matches a UHMS or CUHMA-recognized diagnosis and document the evidence base in the chart.
- Screen for untreated pneumothorax with chest imaging within 30 days.
- Review cardiac history and obtain recent ECG plus echocardiogram if heart disease is known.
- Perform otoscopy and refer to ENT if tympanic mobility is abnormal or equalization is poor.
- Reconcile medications against the HBOT-interaction list; consult the receiving physician on timing.
- Document diabetes status with recent HbA1c and glucose self-monitoring pattern.
- Assess psychological tolerance for confined space and extended treatment course.
- Identify implanted devices and confirm pressure ratings with the manufacturer.
- Review coverage and facility choice using the provincial coverage guide and facilities directory.
- Submit the referral with imaging, medication list, recent labs, and the indication-specific documentation requested by the receiving centre.
Frequently Asked Questions from Canadian Referring Physicians
Can I refer a patient who is actively receiving chemotherapy?
Yes, but coordinate with the oncologist. Most centres avoid HBOT for patients receiving bleomycin or cisplatin in the same cycle. For other chemotherapy regimens, decisions are individualized. Always include the chemotherapy regimen, dose, and schedule in the referral.
Does the patient need a chest x-ray every time?
Most centres require imaging within 30 days of initiation. A single baseline chest x-ray is usually sufficient for patients without pulmonary risk factors. Repeat imaging is indicated if the patient develops new respiratory symptoms during the course.
Is HBOT safe for patients with pacemakers or implantable cardioverter-defibrillators?
Most modern devices are pressure-rated to at least 3.0 atmospheres absolute, but confirmation from the manufacturer is required. The receiving centre will typically request the device card or an interrogation report. Flag all implanted devices in the referral.
Should I stop the patient’s anticoagulants?
No. Anticoagulation is not a contraindication to HBOT. The referring physician should continue the patient’s usual regimen and communicate it clearly to the hyperbaric centre.
How long does the pre-referral workup usually take?
A complete workup usually takes one to two weeks for elective indications. Urgent indications such as necrotizing soft tissue infection, decompression sickness, or carbon monoxide poisoning bypass the elective process and proceed through emergency pathways at hospital-based centres.
What provincial health plan covers HBOT?
Each province uses its own plan name. Ontario uses OHIP, British Columbia uses MSP, Alberta uses AHCIP, Quebec uses RAMQ, and the Atlantic provinces use MSI, Medicare NB, PEI Health, and MCP. Publicly funded HBOT is delivered at hospital-based chambers for recognized indications. Check the provincial coverage page for specifics.
When should I refer urgently rather than electively?
Refer urgently for suspected carbon monoxide poisoning, decompression sickness, arterial gas embolism, central retinal artery occlusion within 24 hours of onset, necrotizing soft tissue infection, acute crush injury, and compromised flap or graft. These are time-critical indications where delay worsens outcomes.
Can I find a hyperbaric facility near my patient?
Canada Hyperbarics maintains a current directory of hospitals and regulated facilities offering HBOT in Canada. Visit the facilities directory to find the nearest centre, filter by indication, and review wait times where published.
Where can you learn more about HBOT referral pathways?
Canada Hyperbarics publishes continually updated guidance for referring physicians, including condition-specific guides, research summaries, and a regularly refreshed directory of hospitals and regulated facilities. Review the linked resources below before your next referral.
- Approved and emerging indications in Canada
- Research library of over 14,400 HBOT studies
- Directory of hospitals and regulated facilities
- Health Canada regulatory overview
- Master FAQ for referring physicians
References
- Schiavo S, Brenna CTA, Albertini L, Djaiani G, Marinov A, Katznelson R. Safety of hyperbaric oxygen therapy in patients with heart failure: A retrospective cohort study. PLoS One. 2024;19(2):e0293484. doi:10.1371/journal.pone.0293484
- Nöhl S, Burisch C, Gödde D, Sellmann T. Power under pressure: defibrillation during hyperbaric oxygen therapy – a scoping review. Diving Hyperb Med. 2025;55(4):407-418. doi:10.28920/dhm55.4.407-418
- Edinguele WFOP, Barberon B, Poussard J, Thomas E, Reynier JC, Coulange M. Middle-ear barotrauma after hyperbaric oxygen therapy: a five-year retrospective analysis on 2,610 patients. Undersea Hyperb Med. 2020;47(2):217-228. doi:10.22462/04.06.2020.7
- Moayedi S, Gizaw A, Sweet S, Sethuraman K, Witting M. Pseudoephedrine prophylaxis does not prevent middle ear barotrauma in hyperbaric oxygen therapy. Undersea Hyperb Med. 2025;52(2):101-107. PMID: 40819351
Medical disclaimer: This content is for informational purposes only and does not constitute medical advice. It is intended for Canadian licenced healthcare professionals considering a referral for hyperbaric oxygen therapy. Clinical decisions should be made in consultation with a hyperbaric physician at the receiving centre. Canada Hyperbarics does not provide clinical care and is not a substitute for the screening protocols of individual hospitals and regulated facilities.