Hyperbaric Oxygen Therapy for Crohn's: A Patient Guide

When standard biologics, immunomodulators, and even surgery haven't brought a Crohn's fistula under control, the search for anything that might tip the balance becomes deeply personal. Hyperbaric oxygen therapy for Crohn's disease - the practice of breathing pure oxygen inside a pressurized chamber - has been quietly building a clinical evidence base over the past several years. It's not a cure, and it's not yet mainstream, but the data from published trials and systematic reviews suggest it deserves more attention than the typical "alternative therapy" label implies.

In this article, we walk through what HBOT actually involves, what the best available studies show, who might realistically benefit, and the practical questions worth bringing to your gastroenterologist.

Key Takeaways

• A meta-analysis of 19 studies covering 809 IBD patients found clinical remission rates of 88% for luminal Crohn's and 60% for perianal Crohn's disease (1)
• The HOT-TOPIC trial showed 12 of 20 patients with refractory perianal fistulas achieved clinical response after 40 HBOT sessions (3)
• Standard protocols use 100% oxygen at 2.0 to 2.5 atmospheres for 90 to 120 minutes per session, typically over 4 to 8 weeks (2)
• About 15% of IBD patients receiving HBOT experience mild side effects, most commonly ear pressure discomfort (1)
• Most insurers currently consider HBOT for Crohn's disease investigational, so out-of-pocket cost is a real barrier (8)
• An ongoing Canadian controlled trial (HYPNOTIC, NCT06109961) is expected to provide stronger evidence by 2026 (6)

What Is Hyperbaric Oxygen Therapy (HBOT)?

Hyperbaric oxygen therapy involves breathing 100% oxygen at pressures of 2.0 to 2.5 atmospheres absolute (ATA) inside a sealed, pressurized chamber (1, 2). At these pressures, far more oxygen dissolves into your blood plasma than normal breathing allows, reaching tissues that are inflamed, swollen, or poorly supplied with blood.

How HBOT Works in the Body

Under normal conditions, oxygen travels through the bloodstream bound to hemoglobin in red blood cells. In a hyperbaric chamber, the elevated pressure forces additional oxygen directly into the plasma itself - the liquid part of blood (2). This means oxygen can reach areas where blood flow is compromised, including the chronically inflamed and thickened intestinal walls that characterize Crohn's disease. Beyond simply delivering more oxygen, HBOT appears to suppress pro-inflammatory cytokines and promote anti-inflammatory pathways, essentially shifting the immune environment toward healing rather than ongoing damage (2).

The Hypoxia Connection in Crohn's Disease

Here's where the science gets particularly relevant. Chronic intestinal hypoxia - meaning the gut tissue isn't getting enough oxygen - is a core feature of IBD biology (2). Inflamed intestinal tissue swells, blood vessels are compressed, and the very cells that need oxygen to heal are starved of it. HBOT directly addresses this problem by flooding the tissue with oxygen from the plasma side, bypassing the damaged blood vessels that can't deliver it normally. For those of us who have watched a fistula or a patch of inflammation stubbornly refuse to heal despite every medication in the toolbox, the logic of addressing tissue-level oxygen deprivation is intuitive.

What a Typical HBOT Course Looks Like

Understanding what you're signing up for matters as much as understanding the science. HBOT is not a pill or an infusion you receive during a regular clinic visit - it's a significant time commitment.

Session Length and Frequency

Each session lasts approximately 90 to 120 minutes at pressures of around 2.4 to 2.5 ATA (2). For perianal Crohn's fistulas, protocols typically involve 20 to 40 sessions, usually scheduled 5 days a week over 4 to 8 weeks (2, 3). The HOT-TOPIC trial, one of the best-studied protocols, used 40 sessions over 8 weeks (3). That's a meaningful block of your life dedicated to treatment.

The Patient Experience Inside the Chamber

Chambers come in two types: monoplace (single-person) and multiplace (room-sized, accommodating several patients). In a monoplace chamber, you lie inside a clear acrylic tube. In a multiplace chamber, you sit in a room and breathe oxygen through a mask or hood. Most people describe the experience as uneventful - you can read, watch content on a device, or sleep. The most noticeable physical sensation is pressure in the ears as the chamber pressurizes, similar to what you feel during airplane descent. You equalize by swallowing or yawning, and the staff will walk you through techniques before your first session.

For patients who experience claustrophobia, it's worth asking the center about their chamber type. Multiplace chambers feel much more open. Some centers also allow mild sedation for anxious patients - a conversation to have with your treatment team before your first appointment.

What the Evidence Shows for Crohn's Disease

The evidence base for HBOT in Crohn's is growing, though it's important to be transparent about where it stands: we have promising data from case series, retrospective studies, one landmark prospective trial, and one systematic review with meta-analysis. What we don't yet have is a large, randomized, placebo-controlled trial - though one is underway.

HBOT for Perianal Fistulas: The HOT-TOPIC Trial

The strongest single study is the HOT-TOPIC trial, published in the United European Gastroenterology Journal in 2022 (3). This prospective study enrolled 20 patients with treatment-refractory perianal Crohn's fistulas - meaning their fistulas had not responded to biologics, antibiotics, or surgical approaches. Each patient received 40 HBOT sessions over 8 weeks at 2.4 ATA. At one-year follow-up (week 60), 12 of 20 patients showed a clinical response, and several achieved complete fistula closure (3).

For anyone who has lived with a perianal fistula, those numbers carry real weight. These were patients for whom standard treatments had already failed. A 60% response rate in that refractory population is notable.

HBOT for Luminal Crohn's Inflammation

The McCurdy systematic review and meta-analysis, published in Inflammatory Bowel Diseases in 2022, pooled data from 19 studies covering 809 IBD patients (1). For luminal Crohn's disease specifically, the analysis found a clinical remission rate of 88% - a striking number, though it's important to note that many of the included studies were case series and retrospective reviews rather than controlled trials (1). For perianal Crohn's, the pooled remission rate was 60% (1).

A 2024 study published in the Journal of Translational Medicine added another dimension: beyond reducing CRP levels and lowering CDAI scores, HBOT appeared to increase gut microbial diversity in Crohn's patients (4). This is intriguing because reduced microbial diversity is one of the hallmark features of IBD, as we've explored in our piece on gut microbiome diversity in Crohn's disease. Whether HBOT truly reshapes the microbiome in a lasting, clinically meaningful way remains to be confirmed, but the signal is worth following.

Postoperative and Emerging Evidence

A 2025 study by Krstulovic and colleagues in Healthcare examined HBOT as an adjunct to conservative treatment in Crohn's disease and reported that 94.1% of conservatively treated patients achieved remission after adjunctive HBOT (5). Perhaps more practically, the reoperation rate was 6.5% in the HBOT group compared to 18.4% in untreated controls (5). For patients considering the role of surgery in Crohn's disease management, the possibility of a therapy that might reduce the need for repeat operations is compelling.

The HYPNOTIC pilot trial (NCT06109961), sponsored by the Ottawa Hospital Research Institute, is the first controlled Canadian study of HBOT for refractory perianal Crohn's disease (6). It's expected to report results by 2026, and its controlled design will provide much stronger evidence than the observational data we currently rely on.

Who Might Be a Candidate for HBOT?

Not every Crohn's patient is a realistic candidate for HBOT. The evidence points to specific situations where it may be most useful - and clear situations where it's not appropriate.

Best-Studied Indications

The strongest evidence supports HBOT for refractory perianal fistulizing Crohn's disease in patients who have not responded adequately to biologics, antibiotics, or surgical drainage (7). This is where the HOT-TOPIC trial and the bulk of case-series data are concentrated. HBOT may also be considered for severe luminal flares that have not responded to standard therapy, though the evidence here is weaker and primarily drawn from retrospective analyses and the McCurdy meta-analysis (7). It's worth understanding that HBOT is generally studied as an adjunctive therapy - something added alongside your existing treatment regimen, not a replacement for it.

When HBOT Is Not Appropriate

Absolute contraindications include untreated pneumothorax (a collapsed lung) and certain chemotherapy drugs that interact dangerously with high-dose oxygen (7). Severe uncontrolled lung disease, including advanced COPD, is also a contraindication. Patients with severe claustrophobia may find monoplace chambers intolerable, though multiplace chambers and pre-treatment anxiolytics can sometimes help. Recent ear surgery, uncontrolled seizure disorders, and certain cardiac conditions require careful screening by the HBOT team before treatment can begin.

Safety, Side Effects, and Real-World Risks

One of the strengths of the existing HBOT literature is that safety has been reasonably well-tracked, even in studies with small sample sizes.

Common Mild Side Effects

Across IBD studies, approximately 15% of patients experienced minor adverse events (1). The most common is ear discomfort or barotrauma - the same pressure-related ear pain you might feel during a flight, but potentially more pronounced at 2.4 ATA. Most patients learn to equalize effectively within the first few sessions. Sinus congestion, mild fatigue, and temporary visual changes (usually mild nearsightedness) have also been reported (7). These visual changes typically resolve within weeks of completing treatment.

Rare but Serious Risks

Oxygen toxicity seizures are the most-discussed serious risk, but they are exceptionally rare at the pressures and durations used for IBD treatment (7). Sinus and pulmonary barotrauma are possible but uncommon with proper pre-screening. Long-term, repeated HBOT exposure carries a recognized risk of cataract formation, which is one reason most IBD protocols cap total sessions at around 30 to 40 (7). Overall, experts in the field consider HBOT broadly safe and well-tolerated at standard IBD treatment pressures, but the therapy does require proper medical supervision and should only be delivered at accredited facilities.

Cost, Access, and How to Talk to Your Gastroenterologist

Even if the clinical evidence appeals to you, the practical realities of HBOT access can be a barrier - and it's better to understand those barriers upfront than to discover them mid-course.

Insurance and Coverage Realities

In the United States, most private insurers and Medicare currently do not cover HBOT for Crohn's disease, categorizing it as investigational (8). HBOT is an approved treatment for other conditions - such as diabetic foot ulcers and radiation tissue damage - but IBD is not yet on the standard coverage list. Outside the U.S., coverage varies widely by country and healthcare system. Out-of-pocket costs for a full course of 30 to 40 sessions can be substantial, varying by region and chamber type. It's essential to get a clear cost estimate from the HBOT center before committing.

One practical avenue worth exploring: clinical trials. The HYPNOTIC trial (6) and others currently enrolling may provide access to HBOT at no cost to the patient, along with close monitoring and follow-up. Your gastroenterologist or a clinical trial database search at clinicaltrials.gov can help identify opportunities near you.

Questions to Bring to Your IBD Team

Walking into an appointment with specific questions gets you further than a general "what do you think about HBOT?" Here are concrete starting points:

• Is my fistula or flare a reasonable indication for HBOT given the current evidence?
• Have we exhausted the standard therapies that are better studied for my situation?
• Are there clinical trials I might qualify for?
• How will we measure whether HBOT is actually helping - what endpoints should we track?
• What's the plan if HBOT doesn't produce results after a defined number of sessions?
• Can you refer me to a UHMS-accredited (Undersea and Hyperbaric Medical Society) center?

HBOT fits within a broader landscape of complementary and adjunctive therapies for Crohn's disease, and your gastroenterologist can help you evaluate where it sits relative to other options for your specific disease pattern.

Frequently Asked Questions

Is hyperbaric oxygen therapy a cure for Crohn's disease?

No. HBOT is studied as an adjunctive therapy, meaning it's used alongside standard treatments like biologics and immunomodulators. The evidence shows it can help reduce inflammation and promote fistula healing, but it does not address the underlying autoimmune process that drives Crohn's disease. It's best understood as another tool in the treatment toolbox, not a standalone solution.

How many HBOT sessions does it take to see results?

Most clinical protocols for Crohn's disease use 20 to 40 sessions over 4 to 8 weeks (2, 3). In the HOT-TOPIC trial, patients received 40 sessions before outcomes were assessed (3). Some patients report subjective improvement earlier, but clinical response is typically measured after the full course is completed. Your treatment team should define clear endpoints before you begin.

Does HBOT hurt?

The treatment itself is not painful. The most common sensation is pressure in the ears during chamber pressurization - similar to descending in an airplane. Staff will teach you equalization techniques before your first session. About 15% of patients experience mild ear discomfort during treatment (1), but serious pain is uncommon and should be reported to the chamber operator immediately.

Can I get HBOT while on biologics like infliximab or adalimumab?

Yes - in fact, most of the clinical studies of HBOT for Crohn's disease enrolled patients who were already on biologics and other standard therapies. HBOT was studied specifically as an addition to existing treatment in refractory cases (3, 7). Your gastroenterologist can advise on scheduling sessions around your infusion or injection schedule.

Is HBOT covered by insurance for Crohn's disease?

In most countries, HBOT for Crohn's disease is not currently covered by standard insurance because it's considered investigational (8). Some patients access HBOT through clinical trials at no cost. Coverage policies vary by insurer and by country, so it's worth checking with your specific plan and asking the HBOT center about payment options before starting treatment.

Are there any long-term risks of HBOT?

The most documented long-term risk is cataract formation with extended or repeated courses of treatment, which is why most IBD protocols limit total sessions to 30 to 40 (7). Oxygen toxicity seizures are exceptionally rare at IBD-standard pressures. Most short-term side effects - ear pressure, fatigue, temporary visual changes - resolve within weeks of completing treatment. Long-term safety data specific to IBD patients is still limited, which is another reason controlled trials like the HYPNOTIC study are important.

What should I ask my doctor before starting HBOT?

Start with whether your specific disease pattern matches the populations studied in HBOT research - refractory perianal fistulas have the strongest evidence (3, 7). Ask whether you've exhausted better-studied standard therapies first, whether there are clinical trials you might qualify for, and what endpoints your team will use to measure success. Request a referral to a UHMS-accredited center, and get a clear cost estimate before committing.

References

1. McCurdy, J., et al. The Effectiveness and Safety of Hyperbaric Oxygen Therapy in Various Phenotypes of Inflammatory Bowel Disease: Systematic Review With Meta-analysis. Inflammatory Bowel Diseases, 2022;28(4):611. Read study
2. Dulai, P. The Potential Role of Hyperbaric Oxygen Therapy in Patients With Inflammatory Bowel Disease. Gastroenterology & Hepatology, December 2024. Read article
3. Lansdorp, C., et al. Hyperbaric oxygen therapy for the treatment of perianal fistulas in 20 patients with Crohn's disease: Results of the HOT-TOPIC trial after 1-year follow-up. United European Gastroenterology Journal, 2022. View on PubMed
4. Li, Sun, Lai, et al. Hyperbaric oxygen therapy ameliorates intestinal and systematic inflammation by modulating dysbiosis of the gut microbiota in Crohn's disease. Journal of Translational Medicine, May 2024. View on PubMed
5. Krstulovic, et al. Hyperbaric Oxygen Therapy in the Treatment of Crohn's Disease. Healthcare 2025;13(2):128. Read study
6. Ottawa Hospital Research Institute. Hyperbaric Oxygen Therapy for Perianal Fistulizing Crohn's Disease Not Responsive or Intolerant to Conventional Care: HYPNOTIC Pilot Study (NCT06109961). View on ClinicalTrials.gov
7. WebMD. Hyperbaric Oxygen Therapy and Crohn's Disease. 2024. Read article
8. Hyperbaric Oxygen Therapy for Refractory Perianal Crohn's Disease: A Case Report. PMC, 2024. Read article