Inflammatory Bowel Disease: The Role of Hyperbaric Oxygen Therapy

Key Takeaways

• Inflammatory bowel disease (IBD) mainly includes ulcerative colitis and Crohn’s disease. Both are chronic, relapsing inflammatory conditions that can cause abdominal pain, diarrhoea, rectal bleeding, fatigue, weight loss and significant disruption to daily life. ¹
• Hyperbaric oxygen therapy (HBOT) is a medically supervised treatment in which patients breathe near-100% oxygen inside a pressurised chamber. This substantially increases the amount of oxygen dissolved in blood plasma and increases oxygen availability to body tissues. ^{2 3}
• There is a strong biological rationale for investigating HBOT in IBD. Inflamed bowel tissue can become relatively hypoxic because of increased oxygen demand, swelling and impaired microvascular function. HBOT may influence tissue oxygenation, inflammatory signalling, epithelial repair, angiogenesis and the local microbial environment. ^{3 4 5}
• The most developed controlled evidence relates to hospitalised moderate-to-severe ulcerative colitis flares. Small clinical trials have investigated short courses of HBOT alongside intravenous corticosteroids, with encouraging early findings. ^{6 7}
• In Crohn’s disease, prospective research has focused particularly on refractory perianal fistulas. The HOT-TOPIC study reported improvements in clinical and radiological outcomes following HBOT that were broadly maintained at one year. ⁸
• Research has also explored luminal and stricturing Crohn’s disease, although the evidence in these settings remains at an earlier stage. ^{9 10}
• Systematic reviews have reported encouraging outcomes across several IBD presentations and generally favourable tolerability. However, the evidence remains limited by small studies, variable protocols and a lack of large confirmatory trials. ^{3 4 5}
• HBOT is being investigated as an adjunct to established IBD care, not as a replacement for gastroenterology-led medical, nutritional, endoscopic or surgical treatment. ^{1 11 12}

Quick Summary

Inflammatory bowel disease is a lifelong condition characterised by recurrent inflammation of the digestive tract. Ulcerative colitis affects the colon and rectum, while Crohn’s disease can involve any part of the gastrointestinal tract and may extend through the full thickness of the bowel wall.

Modern medical and surgical treatments have transformed IBD care. However, some people continue to experience active inflammation, steroid dependence, loss of response to treatment or difficult complications such as strictures, abscesses and fistulas. This has led researchers to investigate adjunctive approaches that work through different biological pathways.

HBOT is one such area of research. Rather than targeting a single immune pathway, HBOT temporarily and substantially increases the amount of oxygen available within the body. This is particularly relevant because actively inflamed bowel tissue can become relatively hypoxic. Researchers are investigating whether improving tissue oxygenation can influence inflammation, microcirculation, intestinal barrier repair, wound healing and the local microbial environment.

The clinical evidence is most developed in hospitalised ulcerative colitis, with prospective research also supporting further investigation in refractory perianal Crohn’s disease. Smaller studies have explored other difficult-to-treat forms of IBD.

The findings are encouraging and provide a credible scientific basis for continued clinical research. At present, however, HBOT remains an emerging adjunct rather than an established treatment for IBD.

What Is Hyperbaric Oxygen Therapy?

Hyperbaric oxygen therapy is a medically supervised treatment in which a patient breathes near-100% oxygen inside a chamber pressurised above normal atmospheric pressure.

Under these conditions, substantially more oxygen dissolves directly into blood plasma. This increases the amount of oxygen available for delivery throughout the body, including to areas where inflammation, swelling or impaired microcirculation may have reduced normal oxygen supply. ^{2 3}

HBOT also produces physiological effects beyond simply increasing blood oxygen levels. Research has described effects on inflammatory signalling, vascular function, hypoxia-response pathways and biological processes involved in tissue repair. ^{3 4 5}

Treatment protocols in IBD research have varied according to the clinical situation. Trials involving hospitalised ulcerative colitis have generally investigated short courses over consecutive days, while studies of chronic, refractory Crohn’s disease complications have used longer courses. ^{6 7 8 9}

These research protocols should not be interpreted as universal treatment recommendations. Any course of HBOT requires individual medical assessment and should be considered in the context of the patient’s disease, current treatment and wider clinical care.

Why Is Oxygen Relevant to IBD?

The relationship between oxygen and intestinal inflammation is an important area of IBD research.

During active inflammation, immune cells consume increased amounts of oxygen. At the same time, swelling and disruption of the small blood vessels supplying the bowel can make oxygen delivery less efficient. As a result, inflamed intestinal tissue may become relatively hypoxic.

This matters because low-oxygen conditions can influence inflammatory signalling, immune-cell behaviour, intestinal barrier integrity, tissue repair and the microbial environment. Hypoxia may therefore be more than a consequence of inflammation. Researchers are investigating whether it also contributes to processes that allow inflammation and impaired healing to persist.

HBOT may influence several of these interconnected pathways:

• Increasing tissue oxygenation, including in areas affected by inflammation or impaired microcirculation.
• Modulating inflammatory signalling and inflammatory-cell activity.
• Supporting epithelial repair and restoration of the intestinal barrier.
• Supporting angiogenesis, the formation of new small blood vessels in injured tissue.
• Influencing tissue-repair processes relevant to ulceration and fistula healing.
• Potentially affecting the local microbial environment through changes in tissue oxygen availability. ^{3 4 5 10}

These mechanisms provide a strong biological rationale for studying HBOT in IBD. Importantly, biological plausibility is not the same as proven clinical benefit. Further human trials are needed to determine whether these effects translate into meaningful clinical improvements for patients.

What Does the Clinical Evidence Show?

Hospitalised Ulcerative Colitis Flares

The most developed controlled evidence for HBOT in IBD comes from patients hospitalised with moderate-to-severe ulcerative colitis flares. This is an important clinical setting because patients who do not respond adequately to intravenous corticosteroids may require rescue medication or surgery. Researchers have investigated whether adding a short course of HBOT to standard inpatient treatment could improve early response. ^{6 7 13}

A multicentre, randomised, double-blind, sham-controlled trial compared HBOT plus intravenous corticosteroids with sham treatment plus corticosteroids. By day five, 50% of patients receiving HBOT met the study definition of clinical remission, compared with none receiving sham treatment. Fewer patients in the HBOT group also progressed to second-line treatment during their hospital admission. ⁶

A subsequent study involving 20 hospitalised patients found that 55% met the study’s response criteria after three HBOT sessions, with reductions in stool frequency, rectal bleeding and C-reactive protein. Patients receiving five treatment days showed greater improvement than those receiving three. ⁷

These are small studies and cannot establish HBOT as standard treatment. However, the results provide an encouraging controlled clinical signal, particularly because HBOT was studied alongside intravenous corticosteroids rather than instead of established care.

A larger multicentre, randomised, double-blind, sham-controlled trial involving 126 hospitalised patients has been designed to investigate these findings further, including effects on clinical response and the need for rescue treatment or colectomy. ¹⁴

Refractory Perianal Fistulising Crohn’s Disease

Perianal fistulas are among the most difficult complications of Crohn’s disease. They can have a substantial impact on pain, function and quality of life and often require coordinated medical and surgical management.

The prospective HOT-TOPIC study investigated HBOT in 20 adults with therapy-refractory perianal fistulas who remained on stable standard treatment while receiving 40 HBOT sessions. ⁸ At 16 weeks, 60% of patients met the study definition of clinical response and 20% achieved clinical remission. Clinical and MRI findings improved following treatment, and much of the improvement was maintained at one-year follow-up.

The longer-term findings are particularly relevant because fistulising Crohn’s disease can be persistent and difficult to treat. However, HOT-TOPIC did not include a control group. This means it is not possible to determine how much of the observed improvement resulted specifically from HBOT rather than background treatment or other factors.

Importantly, these findings should not be generalised to all fistula types. In the small HOT-REVA pilot study, HBOT used as monotherapy did not result in clinical closure of Crohn’s-related rectovaginal fistulas. ¹⁵ This highlights the importance of fistula phenotype, patient selection and the role of HBOT within a broader multidisciplinary treatment strategy.

Taken together, the evidence provides an important prospective signal for HBOT as an adjunct in refractory perianal fistulising Crohn’s disease, while supporting further controlled investigation alongside established medical and surgical care.

Luminal and Stricturing Crohn’s Disease

HBOT has also been investigated in luminal and stricturing Crohn’s disease, although the evidence here is less developed.

A small prospective pilot study examined HBOT in patients with refractory small-bowel stricturing Crohn’s disease and reported improvements in clinical measures, with radiological improvement observed in some participants who underwent comparative imaging. ⁹ The study was small and uncontrolled, so it cannot establish whether HBOT can alter established fibrosis, prevent obstruction or reduce the need for endoscopic or surgical intervention.

A separate 2024 prospective study investigated HBOT alongside ustekinumab and explored possible effects on inflammation and the gut microbiome. Researchers observed reductions in inflammatory measures within the HBOT group together with changes in microbial diversity and composition. ¹⁰

Although some early clinical outcomes numerically favoured HBOT, between-group differences in clinical response and remission did not reach statistical significance. These studies broaden the scientific rationale for HBOT in Crohn’s disease, particularly around inflammation, tissue oxygenation and the intestinal microbiome. At present, however, the evidence is not sufficient to establish clinical effectiveness in luminal or stricturing disease. Suspected bowel obstruction, abscess, perforation or another acute Crohn’s complication requires appropriate urgent assessment and should never be delayed for HBOT.

What Do Systematic Reviews Tell Us?

Several systematic reviews and meta-analyses have brought together the clinical evidence for HBOT across different forms of IBD.

A 2021 systematic review and meta-analysis identified 18 studies and reported encouraging pooled response findings in both ulcerative colitis and Crohn’s disease. The authors concluded that the evidence supported further investigation of HBOT, while highlighting the need for appropriately designed randomised trials. ³

A 2022 systematic review by McCurdy and colleagues included 19 studies involving 809 patients. It reported substantial rates of clinical remission across several IBD phenotypes, including ulcerative colitis and perianal Crohn’s disease. However, only three studies were randomised trials and most of the included evidence was considered low quality because of absent comparator groups, incomplete reporting of concurrent treatments or a lack of objective outcomes. ⁴

A further 2022 meta-analysis compared HBOT plus usual care with usual care alone. Across the included ulcerative colitis studies, the addition of HBOT was associated with a higher likelihood of clinical response. The authors nevertheless concluded that further studies were required to establish optimal treatment protocols and strengthen the evidence base. ⁵

Taken together, these reviews strengthen the overall clinical signal but also highlight an important distinction: promising pooled outcomes do not carry the same evidential weight as large, well-controlled clinical trials. The evidence is currently most developed in hospitalised ulcerative colitis and refractory perianal Crohn’s disease. Larger controlled studies are needed to establish which patients are most likely to benefit, the optimal treatment protocol and whether HBOT can improve longer-term outcomes.

Where Could HBOT Fit Within IBD Care?

The emerging evidence positions HBOT as a potential adjunct to established IBD care.

Current management may include aminosalicylates, corticosteroids, immunomodulators, biologic or small-molecule therapies, nutritional support, antibiotics, endoscopic procedures and surgery. ^{1 11 12} HBOT works through different biological pathways, with research exploring its effects on tissue oxygenation, inflammation, microcirculation and repair.

Where HBOT is considered, it should form part of a coordinated treatment plan with a clear clinical objective. Response can be assessed using measures appropriate to the individual patient, such as symptoms, inflammatory markers, endoscopy, MRI or fistula healing. HBOT should complement, rather than delay, established medical or surgical treatment when this is clinically required.

What Does Treatment Involve?

The HBOT protocols used in IBD research differ according to the condition being studied.

For hospitalised ulcerative colitis flares, clinical trials have generally investigated approximately three to five consecutive sessions, commonly lasting around 90 minutes, alongside intravenous corticosteroids and standard inpatient treatment. ^{6 7}

For chronic or refractory Crohn’s disease complications, research has generally used longer courses. The HOT-TOPIC study, for example, investigated 40 sessions in patients with refractory perianal fistulas. ⁸

These protocols come from clinical research and are not universal treatment recommendations. The appropriate approach depends on the individual patient, disease phenotype, clinical presentation, previous treatment and stage of care. Any HBOT programme should therefore begin with an individual medical assessment and, where appropriate, be coordinated with the gastroenterology and surgical teams involved in the patient’s care.

Safety and the Evolving Evidence

HBOT has generally been reported as well tolerated in published IBD studies. Systematic reviews have found relatively low rates of treatment-related adverse events, although the available safety evidence remains limited by the size and quality of the underlying studies. ^{3 4 5}

As with any medical treatment, appropriate patient selection is important. ¹⁶ Suitability for HBOT should be assessed by a clinician experienced in hyperbaric medicine, taking into account the patient’s medical history, current treatment and relevant contraindications. ¹⁷ For people with IBD, this assessment should sit within a coordinated clinical plan alongside their gastroenterology care.

Research into HBOT for IBD has progressed from early case reports and mechanistic studies towards prospective cohorts and controlled clinical trials. ^{6 7 8 9 10 13 18} The focus is increasingly on where HBOT may provide meaningful additional benefit, which patients are most likely to respond and how it can best be integrated with established treatment.

Important questions remain around patient selection, treatment timing, optimal protocols and the durability of response. Future studies will also need to examine outcomes that matter most to patients, including sustained symptom control, mucosal healing, fistula healing, quality of life and the need for treatment escalation or surgery.

The biological rationale is strong, and early clinical findings in selected patient groups are encouraging. HBOT is already being used as an adjunct in selected clinical settings, including alongside specialist gastroenterology care. Larger, well-designed trials will help determine which patients are most likely to benefit, establish optimal treatment protocols and clarify whether HBOT should become a more routinely integrated part of IBD care.

Summary

Hyperbaric oxygen therapy is an emerging area of clinical research in inflammatory bowel disease.

There is a strong biological rationale for its investigation because active intestinal inflammation can create a relatively hypoxic and microvascularly disturbed tissue environment. Increasing tissue oxygen availability may influence inflammatory signalling, intestinal barrier repair, vascular responses and the local microbial environment.

The most developed controlled evidence relates to hospitalised moderate-to-severe ulcerative colitis, where small trials have reported encouraging early outcomes when HBOT was added to intravenous corticosteroids.

In perianal fistulising Crohn’s disease, prospective research has reported favourable clinical and radiological findings in patients with difficult-to-treat disease, including improvements maintained at one year.

Research in other forms of Crohn’s disease remains at an earlier stage.

Systematic reviews reinforce these encouraging signals, but also highlight the limitations of the evidence. Studies remain relatively small, treatment protocols vary and large confirmatory trials are still needed. HBOT should therefore be understood as an investigational or emerging adjunct in IBD care, rather than an established treatment for the condition. Its potential lies in complementing established gastroenterology care through a different biological pathway, particularly in selected clinical situations where inflammation, tissue hypoxia and difficult healing remain important challenges.

HBOT should complement, not replace or delay, established medical, endoscopic or surgical treatment. Anyone considering HBOT should discuss its potential role with their gastroenterology team and an appropriately qualified clinician with expertise in hyperbaric medicine.

References