Hyperbaric Oxygen Therapy Research: Clinical Evidence & Study Findings

HBOT has 14 FDA-cleared indications and a clinical research base spanning more than 100 conditions. A 2024 meta-analysis of 14 studies found HBOT increased complete wound healing by 2.39 times compared with standard care. In aging research, 60 sessions at 2.0 ATA lengthened telomeres by more than 20% and reduced senescent cells by up to 37%. This page maps the evidence by strength, cites the key studies, and flags the limitations honest reporting requires.

The research landscape for HBOT has expanded since 2020. Studies on telomere lengthening, stem cell mobilization, and neuroplasticity have pushed hyperbaric oxygen therapy beyond its wound-healing roots into regenerative medicine, neurology, and longevity. Not all of that evidence is equal. Some conditions have decades of randomized controlled trials behind them. Others rest on pilot studies or case reports.

How to read the evidence tiers

Throughout this page, each condition is rated on a four-tier scale. The tier reflects study design and volume, not whether individual patients report benefit.

HBOT research by condition

Here is a quick-reference table of the current evidence level for the most commonly studied HBOT applications. Our depression and mental health page goes deeper on the neuropsychiatric research.

Condition	Evidence Level	Key Studies	Typical Protocol
Chronic non-healing wounds (diabetic foot ulcers)	Strong (FDA-cleared)	Londahl et al. 2010, Oley et al. 2024	2.0-2.4 ATA, 30-40 sessions
Decompression sickness	Strong (FDA-cleared)	UHMS guidelines	2.4-2.8 ATA, emergency protocol
Carbon monoxide poisoning	Strong (FDA-cleared)	Weaver et al. 2002 (NEJM)	2.4-3.0 ATA, 1-3 sessions
Delayed radiation injury	Strong (FDA-cleared)	Cardinal et al. 2018, Feldmeier et al. 2024	2.0-2.4 ATA, 20-40 sessions
Necrotizing soft tissue infections	Strong (FDA-cleared)	Hedetoft et al. 2021	2.0-2.5 ATA, adjunctive
Traumatic brain injury / Concussion	Emerging	Harch et al. 2012, Hadanny et al. 2022	1.5-2.0 ATA, 40-60 sessions
Stroke recovery	Emerging	Efrati et al. 2013	2.0 ATA, 40-60 sessions
Anti-aging / Telomere lengthening	Emerging	Hachmo et al. 2020 (Aging)	2.0 ATA, 60 sessions
Stem cell mobilization	Emerging	Thom et al. 2006 (AJP)	2.0 ATA, 20 sessions
Fibromyalgia	Moderate	Efrati et al. 2015	2.0 ATA, 40 sessions
Long COVID	Moderate	Zilberman-Itskovich et al. 2022, Tanaka et al. 2024	2.0 ATA, 40 sessions
IBD (Crohn’s / Ulcerative colitis)	Moderate	Dokmak et al. 2023	2.0-2.4 ATA, 30-40 sessions
Autism spectrum disorder	Limited	Rossignol et al. 2009	1.3-1.5 ATA, 40 sessions
Depression / Anxiety	Limited	Secondary-outcome data (e.g. Efrati et al. 2015)	2.0 ATA, 40-60 sessions
Fertility (poor ovarian reserve)	Limited	Pre-post cohort, 2025	1.5-2.0 ATA, 4-7 sessions

Which HBOT uses have the strongest evidence?

The strongest evidence sits with the 14 FDA-cleared indications, supported by decades of data, multiple randomized controlled trials, and systematic reviews. Insurance typically covers HBOT for these when other treatment options have failed. The full list is maintained in the UHMS approved indications.

Chronic non-healing wounds and diabetic foot ulcers

Wound healing is the most robustly studied HBOT application. Pressurized oxygen stimulates angiogenesis, enhances white blood cell function, and promotes collagen synthesis in oxygen-deprived tissue. The double-blind HODFU trial by Londahl and colleagues enrolled 94 diabetic patients with chronic foot ulcers and found complete healing in 52% versus 29% placebo (P=0.03) at one year in the evaluable group (Londahl et al., 2010). A 2025 network meta-analysis of 34 RCTs and 2,268 diabetic foot ulcers ranked HBOT first for healing rate among gas therapies (Yang et al., 2025). A 2024 meta-analysis of 14 studies found HBOT increased complete wound healing by 2.39 times (RR 2.39) and reduced major amputations by 69% (RR 0.31, 95% CI 0.18-0.52) (Oley et al., 2024).

For more on this application, see our guide to hyperbaric chamber therapy for wound healing.

Decompression sickness

This is the original use case. When divers ascend too quickly, dissolved nitrogen forms bubbles in blood and tissue. HBOT compresses those bubbles and accelerates nitrogen elimination. The evidence base comes from decades of military medicine, case series, and treatment registries, and UHMS guidelines set the consensus protocol: immediate recompression at 2.4 to 2.8 ATA with additional sessions as needed.

Carbon monoxide poisoning

Weaver and colleagues published a 2002 randomized trial in the New England Journal of Medicine enrolling 152 patients. Three HBOT sessions within 24 hours reduced cognitive sequelae from 46% to 25% at six weeks, a number needed to treat of about 4.8 (Weaver et al., 2002).

Delayed radiation injury

A 2018 scoping review and meta-analysis of 13 studies covering 602 patients found 84% partial or complete resolution of radiation-induced hemorrhagic cystitis (Cardinal et al., 2018). A 2024 Medicare analysis of 3,309 patients found HBOT reduced mortality by 53%, urinary bleeding by 36%, and transfusions by 78%, and saved $11,548 per patient when 40 or more sessions were given (Feldmeier et al., 2024).

Necrotizing soft tissue infections

A 2021 meta-analysis of 21 studies and 48,744 patients found HBOT reduced in-hospital mortality by 56% (OR 0.44, 95% CI 0.33-0.58), the largest dataset assembled for this indication (Hedetoft et al., 2021).

What does the emerging research show?

These conditions lack FDA clearance for HBOT, but the research is expanding and several are candidates for future clearance or insurance coverage expansion.

Traumatic brain injury and concussion

Harch and colleagues published a 2012 study in the Journal of Neurotrauma showing improvements in symptoms, cognitive testing, and SPECT brain imaging in 16 military veterans with blast-induced TBI after 40 sessions at 1.5 ATA (Harch et al., 2012). A 2022 randomized trial by Hadanny and colleagues in children with persistent post-concussion syndrome reported improvements in cognitive function and brain MRI measures (Hadanny et al., 2022). The US Department of Defense has funded a large multi-site trial evaluating HBOT for TBI and PTSD in military populations.

Stroke recovery

Efrati and colleagues published a 2013 study in PLoS ONE reporting neurological improvements in 74 enrolled patients who were 6 to 36 months post-stroke, with SPECT imaging documenting increased brain metabolic activity (Efrati et al., 2013).

Anti-aging and telomere lengthening

A prospective trial by Hachmo, Efrati, and colleagues in the journal Aging enrolled 35 healthy adults over age 64 for 60 daily HBOT sessions at 2.0 ATA. Telomere length in peripheral blood mononuclear cells increased by 20 to 38% depending on cell type, and senescent T-cell populations decreased by about 37.3% without any change in lifestyle, diet, or medication (Hachmo et al., 2020). The caveats matter: 35 participants, no control group, and unknown long-term significance of telomere changes for actual health outcomes. Larger controlled trials are needed. Explore this on our hyperbaric chamber anti-aging page.

Stem cell mobilization

Thom and colleagues showed in a 2006 study in the American Journal of Physiology that a single HBOT session at 2.0 ATA doubled circulating stem progenitor cells (CD34+ cells), and after 20 sessions those levels rose roughly eightfold, about 800% above baseline (Thom et al., 2006).

Which conditions have moderate evidence?

Fibromyalgia

Efrati and colleagues published a 2015 prospective trial with a crossover control in PLoS One, showing HBOT improved pain thresholds, symptom questionnaires, and quality of life in fibromyalgia patients, with brain SPECT changes in pain-processing regions (Efrati et al., 2015). It remains a single-center study requiring replication.

Long COVID

A sham-controlled RCT at Shamir Medical Center near Tel Aviv enrolled 73 patients with post-COVID cognitive symptoms and reported improvements in attention, executive function, and memory, with increased brain perfusion on MRI (Zilberman-Itskovich et al., 2022). A 2024 international registry cohort tracked 149 Long COVID patients receiving HBOT and found Neurobehavioral Symptom Inventory scores dropped from 30.6 to 14.4 (P<0.001) (Tanaka et al., 2024).

Inflammatory bowel disease

A 2023 analysis of 164 IBD patients receiving 5,125 HBOT sessions found 87% overall clinical response in fistulizing Crohn’s disease with 59% complete remission (Dokmak et al., 2023).

Fertility

A 2025 pre-post cohort study of 41 women with poor ovarian reserve found that 4 to 7 HBOT sessions improved oocyte number and embryo quality. Cycles producing no available embryos fell from 58.54% before HBOT to 14.63% after (P<0.001). This is a small uncontrolled study, not an RCT (Reproductive Biology and Endocrinology, 2025).

Why does treatment pressure matter when reading HBOT studies?

Pressure matters because results at one pressure do not transfer to another. This is the most common mistake in evaluating HBOT research.

• 1.3 ATA (soft chambers): FDA-cleared only for altitude sickness. Not considered medical-grade HBOT, and insufficient to significantly raise tissue oxygen for most clinical indications.
• 2.0 ATA: The most common pressure in clinical trials, used in the telomere, fibromyalgia, stroke, and Long COVID studies.
• 2.4-3.0 ATA: Used mainly for emergency indications, with higher oxygen toxicity risk, so treatment durations are shorter.

Results from a 2.0 ATA study do not automatically apply to 1.3 ATA. When evaluating HBOT for any condition, the pressure and number of sessions in the supporting research should match what you would actually receive.

What are the limitations of HBOT research?

• Small sample sizes: Most HBOT trials enroll 30 to 100 participants. Few exceed 200.
• Short follow-up: Many studies measure outcomes immediately after the protocol ends, so long-term durability is often unknown.
• Single-center studies: Much of the most notable research comes from one or two groups, notably Efrati’s team in Israel. Independent replication is essential but often lacking.
• Heterogeneous protocols: Studies vary in pressure (1.3 to 3.0 ATA), session count (10 to 60), and duration (60 to 120 minutes), which makes direct comparison difficult.
• Funding limitations: HBOT cannot be patented, so pharmaceutical companies have little incentive to fund large trials.

How to read an HBOT study

Study design runs from strongest to weakest: systematic reviews and meta-analyses, then RCTs, then observational studies, then case series. Ask how many patients were enrolled, whether there was a control group, whether it was sham-controlled, and what pressure was used. When you see a claim that HBOT is proven to treat a condition, check whether the support is an RCT with 50 or more patients or a case series of 8 people at a clinic that sells HBOT sessions. For a look at reported outcomes across indications, see our HBOT success rate and longevity and performance pages.