HBOT Contraindications: A Screening Guide for Referring Physicians

TL;DR: Hyperbaric oxygen therapy (HBOT) is generally safe, but referring physicians must screen for absolute contraindications – primarily untreated pneumothorax and certain chemotherapy agents – and evaluate relative contraindications such as uncontrolled seizure disorders, severe COPD, and heart failure. This guide provides a step-by-step clinical screening checklist to help Canadian physicians make confident, evidence-based referral decisions.

HBOT contraindications are medical conditions or circumstances that make hyperbaric oxygen therapy potentially unsafe or inappropriate for a patient. Hyperbaric oxygen therapy contraindications are among the most common questions referring physicians have before initiating a patient referral. HBOT is a medical treatment that delivers 100% oxygen at pressures greater than 1 atmosphere absolute (ATA), typically between 2.0 and 2.4 ATA, in a sealed chamber. While the therapy has an established safety profile across its 14 UHMS-approved indications, proper patient screening is essential to minimise adverse events and ensure optimal outcomes.

According to research retrieved from PubMed, the most comprehensive review of HBOT side effects reports that middle ear barotrauma occurs in up to 2% of treated patients, while more serious complications such as oxygen toxicity seizures are rare and typically associated with higher treatment pressures (Camporesi, 2014; PMID: 24984321). This how-to guide walks Canadian referring physicians through each screening step before making an HBOT referral.

Estimated reading time: 8 minutes

How Do You Distinguish Between Absolute and Relative HBOT Contraindications?

Before screening a patient, it is important to understand the two categories of contraindications. Absolute contraindications are conditions where HBOT must not be administered under any circumstances. Relative contraindications are conditions that increase risk but may still permit treatment with appropriate precautions, monitoring, and specialist consultation.

The Canadian Undersea and Hyperbaric Medical Association (CUHMA) and the Undersea and Hyperbaric Medical Society (UHMS) both recognise this two-tier classification system. The treating hyperbaric physician makes the final determination, but the referring physician plays a critical role in identifying potential contraindications before referral.

Step 1: Screen for Absolute Contraindications

The following conditions represent situations where HBOT must not proceed. Review each item with your patient before initiating a referral.

Key point: Untreated pneumothorax is the only universally agreed absolute contraindication. Chemotherapy-related contraindications vary by centre and drug, so always confirm with the receiving hyperbaric facility. As noted in a comprehensive review by Ortega et al. (2021), these contraindications are well established across international guidelines (DOI: 10.3390/medicina57090864).

Step 2: Evaluate Relative Contraindications

Relative contraindications require careful risk-benefit analysis and may require additional workup, specialist consultation, or modified treatment protocols.

A 2024 Canadian study conducted at Toronto General Hospital specifically examined HBOT safety in heart failure patients. Of 23 patients with heart failure (including those with reduced ejection fraction), 21 completed treatment without complications. The two patients who developed symptoms were managed with diuretic adjustment, and one went on to complete 33 sessions uneventfully (Schiavo et al., 2024; DOI: 10.1371/journal.pone.0293484). This study demonstrates that heart failure is a manageable relative contraindication rather than an absolute barrier to treatment.

Step 3: Assess Common Side Effects and Risk Profile

Understanding the side effect profile helps set appropriate patient expectations and informs your referral documentation. Based on articles retrieved from PubMed, the established side effects of HBOT include:

1. Middle ear barotrauma – the most common side effect, occurring in up to 2% of patients. Prevented or minimised by teaching autoinflation techniques or inserting tympanostomy tubes (Camporesi, 2014).
2. Transient myopia – progressive short-sightedness that develops during extended treatment courses, typically reversible within weeks to months after completing HBOT.
3. Claustrophobia – affects patients in both monoplace and multiplace chambers. Manageable with reassurance, coaching, and occasionally sedation.
4. Pulmonary oxygen toxicity – rare, presents as cough and inspiratory discomfort. Risk increases with prolonged or high-pressure exposures.
5. Oxygen toxicity seizures – rare, estimated at fewer than 1 in 10,000 treatments at standard clinical pressures. More common in acidotic patients during emergency treatments.

Mackay et al. (2025) identified four critical patient selection criteria for HBOT: glycaemic control, evaluation of contraindications, ulcer severity, and resistance to first-line treatments. While their review focused on diabetic foot ulcers, these patient selection principles apply broadly to all HBOT referrals (DOI: 10.1016/j.jdiacomp.2025.108973).

Step 4: Complete the Pre-Referral Screening Checklist

Use this checklist before sending your referral to the hyperbaric facility. Include the results in your referral documentation.

1. Confirm the indication: Is the patient’s condition among the 14 UHMS-approved indications or an emerging indication with supporting evidence?
2. Review chest imaging: Rule out pneumothorax. If the patient has had recent thoracic surgery, CT, or trauma, obtain a current chest X-ray.
3. Obtain medication history: Screen for bleomycin, cisplatin, doxorubicin, disulfiram, and mafenide acetate. Note any current chemotherapy regimen.
4. Assess cardiac status: If the patient has known heart failure, document current LVEF, fluid balance status, and diuretic regimen.
5. Evaluate seizure history: If present, document current anti-seizure medications and last seizure date.
6. Screen respiratory function: For patients with COPD or chronic respiratory disease, obtain a recent ABG or pulmonary function test.
7. Check ear, nose, and throat status: Identify active upper respiratory infections, chronic sinusitis, or prior ear surgery.
8. Document implanted devices: List pacemakers, cochlear implants, or other implanted medical devices with model numbers.
9. Assess pregnancy status: For patients of childbearing age, confirm pregnancy status.
10. Note diabetes management: For diabetic patients, document recent HbA1c and current glycaemic control regimen.

Step 5: Initiate the Referral

Once screening is complete, send the referral to an accredited hyperbaric facility. In Canada, you can locate facilities through the Canada Hyperbarics clinic directory or through CUHMA’s member directory. Include the following in your referral package:

• Completed screening checklist results
• Current medication list
• Relevant imaging and lab work
• Clinical indication with supporting documentation
• Provincial health plan information (for coverage eligibility)

The receiving hyperbaric physician will conduct their own evaluation, including a focused history and physical examination, before initiating treatment. Your screening documentation helps expedite this process and ensures no contraindications are missed in the transition of care.

For a complete overview of which conditions are approved for HBOT and the current evidence base, visit our research database, which indexes thousands of peer-reviewed studies.

Frequently Asked Questions

What is the most common contraindication for hyperbaric oxygen therapy?

Untreated pneumothorax is the only universally recognised absolute contraindication for HBOT. The expansion of trapped air during decompression can cause a tension pneumothorax. Once a chest tube is placed, HBOT may proceed. Beyond pneumothorax, concurrent bleomycin use is the most commonly cited absolute contraindication in clinical practice.

Can patients with pacemakers receive HBOT?

Many modern pacemakers and implantable cardiac defibrillators are rated for pressures encountered during HBOT (typically 2.0–3.0 ATA). However, the referring physician should verify the specific device’s pressure rating with the manufacturer before referral. The hyperbaric team will confirm device compatibility during their pre-treatment assessment.

Is HBOT safe during pregnancy?

HBOT is generally avoided during pregnancy due to limited safety data and theoretical risk of retrolental fibroplasia in the developing foetus. The exception is life-threatening carbon monoxide poisoning, where the risk of untreated CO exposure to both mother and foetus outweighs the theoretical risks of HBOT.

How often do oxygen toxicity seizures occur during HBOT?

Oxygen toxicity seizures during HBOT are rare, estimated at fewer than 1 in 10,000 patient treatments at standard clinical pressures of 2.0–2.4 ATA. Risk is higher in acidotic patients and at pressures above 2.5 ATA. Seizures during HBOT are self-limiting once oxygen delivery is reduced and do not cause lasting neurological damage.

Should I stop blood thinners before an HBOT referral?

Anticoagulant therapy is not a contraindication to HBOT. Patients on warfarin, direct oral anticoagulants (DOACs), or antiplatelet agents may receive HBOT without dose adjustment. However, note the anticoagulation status in your referral, as it may be relevant for any procedures required during treatment.

What about patients with diabetes – are there special considerations?

Diabetes is not a contraindication, but glycaemic control should be optimised before starting HBOT. Hyperbaric oxygen can affect blood glucose levels during treatment. Patients on insulin should monitor glucose before and after each session, and the hyperbaric team will typically have glucose management protocols in place.

Can patients with COPD safely receive HBOT?

Patients with COPD can receive HBOT, but those with severe disease and chronic CO₂ retention require careful evaluation. A baseline arterial blood gas should be obtained before referral. Air breaks during treatment and lower treatment pressures may be used to mitigate risk.

Where can I find the current Health Canada regulatory status of HBOT?

Health Canada regulates hyperbaric chambers as Class III medical devices. For current approved indications and regulatory information, refer to the Health Canada Medical Devices Active Licence Listing (MDALL) database or contact Health Canada directly.

Making Confident HBOT Referral Decisions

Screening for hyperbaric oxygen therapy contraindications is a straightforward process when approached systematically. By reviewing absolute contraindications, evaluating relative risk factors, and completing a thorough pre-referral checklist, Canadian physicians can make confident, evidence-based referral decisions that optimise patient safety.

Canada Hyperbarics provides comprehensive resources to support referring physicians, including our conditions database, national clinic directory, and peer-reviewed research library with thousands of peer-reviewed studies. If you have questions about a specific patient’s eligibility for HBOT, contact the receiving hyperbaric facility directly – they welcome pre-referral consultations.

This content is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider for medical decisions. Clinical protocols may vary between hyperbaric facilities. The information presented here reflects current evidence as of March 2026 and should be verified against the latest clinical guidelines.