TL;DR: Hyperbaric oxygen therapy (HBOT) is emerging as an adjunct for inflammatory bowel disease, with the strongest evidence in hospitalised ulcerative colitis flares, refractory perianal Crohn’s disease, and chronic pouchitis. A multi-centre NIDDK consortium that includes Canadian investigators from McMaster and Western University is now standardising trial design for acute severe UC. Early data show reduced inflammatory markers, improved steroid responsiveness, and favourable microbiome shifts, but long-term efficacy remains unconfirmed.
Hyperbaric oxygen therapy (HBOT) is a medical treatment in which a patient breathes 100% oxygen inside a pressurised chamber, increasing dissolved oxygen delivery to hypoxic tissue. Inflammatory bowel disease is a chronic relapsing-remitting disorder of the gastrointestinal tract that encompasses ulcerative colitis (UC), Crohn’s disease (CD), and indeterminate colitis. Canadian IBD prevalence is among the highest globally, and refractory phenotypes, particularly acute severe UC and perianal fistulizing CD, continue to drive hospitalisation and colectomy rates. This research summary reviews the 2023-2026 literature on hyperbaric oxygen therapy as an adjunctive treatment for IBD, with attention to mechanistic insights, clinical outcomes, trial methodology, and the Canadian research footprint.
What is the biological rationale for HBOT in inflammatory bowel disease?
Mucosal hypoxia is a recognised contributor to chronic intestinal inflammation. Chen and colleagues (2024), in a narrative review published in Precision Clinical Medicine, describe several converging mechanisms through which hyperbaric oxygen therapy is believed to exert an anti-inflammatory effect in IBD: reduction of oxidative stress, suppression of mucosal inflammatory cytokines, acceleration of ulcer re-epithelialisation, and modulation of the gut microbiome (DOI: 10.1093/pcmedi/pbae001). Kaur, Kochhar and Dulai (2023), writing in Current Opinion in Gastroenterology, frame HBOT as pharmacologic delivery of dissolved oxygen to ischaemic mucosa, which partially reverses HIF-1α-driven inflammatory programs (DOI: 10.1097/MOG.0000000000000952).
Key mechanistic claim: HBOT treats IBD not as an antimicrobial or immunomodulator but as a tissue-oxygenation intervention that indirectly modifies immune, microbial, and repair pathways downstream of hypoxia.
What does the evidence show for hospitalised ulcerative colitis flares?
Two phase 2 trials to date have evaluated HBOT as a rescue adjunct in hospitalised UC. Both demonstrated improved steroid responsiveness and reduced need for infliximab rescue or colectomy within the index admission. These findings motivated the NIDDK HBOT-UC Consortium, a multi-centre effort that in 2024 published a pragmatic trial methodology paper (Dulai et al., Alimentary Pharmacology and Therapeutics) addressing disease activity measurement, endoscopy requirements, standardised steroid dosing, patient-reported outcomes, and sample size challenges in this orphan population (DOI: 10.1111/apt.18326).
The consortium recommends that the Truelove and Witts criteria not be used in isolation, that endoscopy define the eligible population, and that primary outcomes incorporate both rectal bleeding and stool frequency, with secondary measurement of urgency and nocturnal bowel movements. Canadian investigators on the consortium include Neeraj Narula (McMaster University, Farncombe Family Digestive Health Research Institute) and Vipul Jairath (Western University, Lawson Health Research Institute).
How effective is HBOT in refractory perianal Crohn’s disease?
Perianal fistulizing Crohn’s disease is difficult to treat: only about a third of patients maintain durable fistula closure with anti-TNF therapy, so most experience recurrent or refractory disease. Singh and colleagues (2024), in a comprehensive Inflammatory Bowel Diseases review, position HBOT alongside mesenchymal stem cells and exclusive enteral nutrition as adjunctive therapies under active investigation (DOI: 10.1093/ibd/izad195).
A 2025 retrospective cohort from Mayo Clinic Rochester (Hajjar et al., Journal of Clinical Medicine) provides the most recent real-world data. Six patients with refractory perianal CD received between 10 and 40 HBOT sessions. Four reported symptomatic improvement, but objective improvement on examination or imaging was documented in only one patient, and five of six ultimately required surgery within a year (DOI: 10.3390/jcm14196843). The authors conclude that HBOT may provide symptomatic relief in some patients with refractory perianal CD but that long-term efficacy data remain limited.
Can HBOT modify the gut microbiome in Crohn’s disease?
Li and colleagues (2024) published the first prospective interventional study pairing HBOT with 16S rRNA sequencing and fecal microbiota transplantation (FMT) in Journal of Translational Medicine (DOI: 10.1186/s12967-024-05317-1). Twenty patients with active Crohn’s disease were allocated to an HBOT group (n=10) or control group (n=10).
Primary findings:
- C-reactive protein fell from 80.79 ± 42.05 mg/L to 33.32 ± 18.31 mg/L (P = 0.004)
- Crohn’s Disease Activity Index fell from 274.87 ± 65.54 to 221.54 ± 41.89 (P = 0.044)
- Microbial diversity increased post-HBOT
- Escherichia relative abundance decreased; Bifidobacterium and Clostridium XIVa increased
- Murine FMT recipients of post-HBOT stool showed reduced colitis severity versus pre-HBOT recipients
- At week 4, more patients on HBOT plus ustekinumab achieved clinical response (70% vs 30%, P = 0.089)
The trial suggests a mechanistic link between HBOT, microbiome restructuring, and systemic inflammation reduction, though the open-label design and small sample size limit generalisability.
What role does HBOT play in chronic pouchitis?
Shen (2024), in a Nature Reviews Gastroenterology and Hepatology review on pouchitis pathophysiology and management, identifies a defined subgroup of chronic antibiotic-refractory pouchitis patients with ischaemic features, fistulae, or abscesses as candidates for hyperbaric oxygen therapy (DOI: 10.1038/s41575-024-00920-5). This reflects the broader pattern across IBD literature: HBOT is most consistently useful where tissue hypoxia, fistulization, or impaired wound healing dominate the phenotype.
How does the current evidence compare across IBD phenotypes?
| IBD Phenotype | Best Evidence Type | Strength of Signal | Key Limitation |
|---|---|---|---|
| Hospitalised acute severe UC | Two phase 2 RCTs; NIDDK consortium trial underway | Moderate | Small samples; heterogeneous endpoints |
| Perianal fistulizing Crohn’s disease | Cohort studies; 2025 Mayo retrospective | Weak to moderate | No controlled trials; subjective outcomes |
| Active Crohn’s disease (mucosal) | Open-label interventional (Li 2024) | Preliminary | n=20; open label; no blinding |
| Chronic pouchitis with ischaemia/fistulae | Case series; expert review | Weak | No prospective trial data |
What are the methodological gaps in the IBD-HBOT literature?
Despite a substantial mechanistic rationale, the clinical trial base remains thin. The Dulai consortium paper identifies several recurring methodological problems that future Canadian and international investigators should address:
- Heterogeneous disease activity definitions, with reliance on the Truelove and Witts criteria alone introducing noise
- Variable pressure and session protocols across studies (2.0 vs 2.4 vs 2.5 ATA; 60 vs 90 vs 120 minute sessions)
- Absence of sham-controlled designs for perianal CD and pouchitis
- Small sample sizes driven by the orphan nature of hospitalised acute severe UC
- Limited long-term follow-up, particularly for refractory perianal disease where the Mayo cohort showed one-year surgical rates near 85%
- Inconsistent patient-reported outcome measurement, with stool frequency, rectal bleeding, urgency, and nocturnal movements variably captured
What are the Canadian research opportunities in IBD-HBOT?
Canada has distinct advantages for advancing this field. Canadian IBD epidemiology, a well-developed hospital-based hyperbaric network (concentrated in Ontario, Quebec, British Columbia, and Alberta), and existing involvement of Canadian investigators in the NIDDK HBOT-UC Consortium position the country to contribute meaningfully. Priority areas include:
- Prospective registry of HBOT use in Canadian IBD patients, linking pressure protocol to outcome
- Pragmatic trials embedded in provincial IBD care pathways, where coverage pathways permit inclusion
- Microbiome substudies paired with clinical response, extending Li et al.’s preliminary findings
- Health economic analysis of HBOT as steroid and biologic rescue in acute severe UC
- Standardisation of sham-controlled protocols for perianal CD
For practitioners and researchers tracking IBD-specific studies, Canada Hyperbarics maintains an indexed research bank with filtered access to PubMed-linked summaries, and a directory of hospitals and regulated facilities across provinces that operate clinical hyperbaric programs suitable for IBD protocols.
Frequently asked questions
Is HBOT currently a Health Canada recognised indication for IBD?
No. HBOT is not a Health Canada-recognised treatment for ulcerative colitis, Crohn’s disease, or pouchitis. All current clinical use in IBD is considered investigational or adjunctive and should be documented as such.
What pressures and session counts are typically used in IBD trials?
Published protocols vary, but hospitalised UC trials have generally used 2.0 to 2.4 ATA sessions of 90 minutes, delivered daily over 5 to 10 days. The Mayo Clinic perianal CD cohort received between 10 and 40 sessions. This protocol variability is one of the core methodological issues the NIDDK consortium is working to standardise.
Are there safety concerns with HBOT in acutely unwell IBD patients?
Published systematic reviews report that HBOT is well tolerated in IBD populations with low rates of adverse events. Standard hyperbaric contraindications still apply, including untreated pneumothorax and certain chemotherapy regimens. Canadian referring clinicians should follow pre-HBOT workup protocols when considering adjunct referral.
Which Canadian centres are actively involved in IBD-HBOT research?
McMaster University (Farncombe Family Digestive Health Research Institute) and Western University (Lawson Health Research Institute) are listed as NIDDK HBOT-UC Consortium collaborators in the 2024 Dulai et al. methodology paper. No Canadian phase 2 or 3 HBOT-IBD trial has been published to date.
Does the microbiome evidence suggest HBOT could replace biologics?
No. Li et al. (2024) explicitly tested HBOT as an adjunct to ustekinumab, not as a replacement. The observed microbiome and inflammation changes are consistent with a synergistic rather than substitutive role.
Where can I find more Canadian HBOT research on other conditions?
The Canada Hyperbarics research bank indexes peer-reviewed HBOT studies across all investigated indications, and the coverage guide documents which provinces currently fund HBOT for recognised indications.
Conclusion
The 2023-2026 literature on hyperbaric oxygen therapy in inflammatory bowel disease reflects a field transitioning from mechanistic plausibility toward rigorous clinical trial infrastructure. The strongest current evidence is in hospitalised acute severe ulcerative colitis, where HBOT appears to improve steroid responsiveness and reduce rescue therapy requirements. Evidence in refractory perianal Crohn’s disease and chronic pouchitis is weaker but biologically coherent. Canadian investigators are positioned to contribute through the NIDDK consortium and through pragmatic registry and health-economic studies grounded in the Canadian hospital hyperbaric network. Researchers tracking this literature can follow updates via the Canada Hyperbarics research bank.
This content is for informational purposes only and does not constitute medical advice. HBOT is not a Health Canada-recognised indication for inflammatory bowel disease; any clinical use in IBD patients should be undertaken under a qualified multidisciplinary team at hospitals and regulated facilities.