Hyperbaric Oxygen Therapy Research: Clinical Evidence & Study Findings

HBOT has 14 FDA-cleared indications and a clinical research base spanning over 100 conditions. A 2024 meta-analysis of 14 studies found HBOT increased complete wound healing by 2.39 times compared to standard care. In aging research, 60 sessions at 2.0 ATA lengthened telomeres by over 20% and reduced senescent cells by up to 37%. This page tracks the full evidence landscape, updated regularly.

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

Below, we break down HBOT research by evidence strength, cite the key studies, and explain the limitations that honest reporting requires.

Evidence Rating Table: HBOT Research by Condition

Before diving into the details, here is a quick-reference table showing the current evidence level for the most commonly studied HBOT applications. Our depression and mental health page breaks this down further.

Condition	Evidence Level	Key Studies	Typical Protocol
Chronic non-healing wounds (diabetic foot ulcers)	Strong (FDA-cleared)	Londahl et al. 2010,1 Oley et al. 20242	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. 2018,4 Feldmeier et al. 20245	2.0-2.4 ATA, 20-40 sessions
Necrotizing soft tissue infections	Strong (FDA-cleared)	Hedetoft et al. 20216	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, Hadanny et al. 2020	2.0 ATA, 40-60 sessions
Anti-aging / Telomere lengthening	Emerging	Efrati et al. 2020 (Aging)7	2.0 ATA, 60 sessions
Stem cell mobilization	Emerging	Thom et al. 2006 (AJP)8	2.0 ATA, 20 sessions
Fibromyalgia	Moderate	Efrati et al. 20159	2.0 ATA, 40 sessions
Long COVID	Moderate	Zilberman-Itskovich et al. 2022,10 Tanaka et al. 202311	2.0 ATA, 40 sessions
IBD (Crohn’s / Ulcerative colitis)	Moderate	Dokmak et al. 202312	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	Efrati et al. 2023 (secondary outcomes)	2.0 ATA, 40-60 sessions
Fertility	Limited	PMC 202513	1.5-2.0 ATA, 4-7 sessions

1. FDA-Cleared Indications: The Strongest Evidence

The FDA has cleared HBOT for 14 medical conditions. These are supported by decades of clinical data, multiple randomized controlled trials (RCTs), and systematic reviews. Insurance typically covers HBOT for these indications when other treatment options have failed. For the complete rundown, see our UHMS approved indications.

Chronic Non-Healing Wounds and Diabetic Foot Ulcers

Wound healing is the most robustly studied HBOT application. The mechanism is well understood: pressurized oxygen stimulates angiogenesis, enhances white blood cell function, and promotes collagen synthesis in oxygen-deprived tissue.

The landmark HODFU double-blind RCT by Londahl and colleagues enrolled 94 diabetic patients with chronic foot ulcers and found complete wound healing in 52% vs 29% placebo (P=0.03) at one year.¹ A 2025 network meta-analysis of 34 RCTs and 2,268 diabetic foot ulcers ranked HBOT first for healing rate (SUCRA=0.814) among all gas therapies.¹⁴ A 2024 meta-analysis of 14 studies found HBOT reduced major amputations by 69% (RR=0.31, 95% CI 0.18-0.52, P<0.00001).²

A 2024 meta-analysis of 14 studies found that HBOT increased complete wound healing by 2.39 times and reduced major amputations by 69% in diabetic foot ulcer patients.”
Oley et al. 2024, Plastic and Reconstructive Surgery Global Open

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

Decompression Sickness

This is the original use case for HBOT. When divers ascend too quickly, dissolved nitrogen forms bubbles in blood and tissue. HBOT works by compressing the gas bubbles and accelerating nitrogen elimination. The evidence base comes from decades of military medicine, case series, and treatment registries. UHMS guidelines represent the consensus protocol: immediate recompression at 2.4-2.8 ATA with additional sessions as needed.

Carbon Monoxide Poisoning

Weaver and colleagues’ 2002 randomized trial in the New England Journal of Medicine enrolled 152 patients and found three HBOT sessions within 24 hours reduced cognitive sequelae from 46% to 25% at six-week follow-up. The number needed to treat was 4.8, making HBOT one of the most effective available interventions.

Delayed Radiation Injury

A 2018 meta-analysis of 13 studies covering 602 patients found 84% partial or complete resolution of radiation-induced hemorrhagic cystitis.⁴ A 2024 Medicare analysis of 3,309 patients found HBOT reduced mortality by 53%, urinary bleeding by 36%, blood transfusions by 78%, and saved $11,548 per patient when 40+ sessions were given.⁵

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).⁶ This represents the largest dataset ever assembled for this indication.

2. Strong Emerging Evidence: The Most Exciting Research

These conditions don’t yet have FDA clearance for HBOT, but the research is compelling and rapidly expanding. Multiple clinical trials are underway, and several conditions are likely candidates for future clearance expansion or insurance coverage expansion.

Traumatic Brain Injury and Concussion

Harch and colleagues published a pivotal 2012 study in the Journal of Neurotrauma showing significant improvements in symptoms, cognitive testing, and SPECT brain imaging in 16 military veterans with blast-induced TBI after 40 sessions at 1.5 ATA. Hadanny and colleagues’ 2022 RCT demonstrated significant improvements in cognitive function, symptom severity, and brain MRI measurements in patients with persistent post-concussion syndrome. The US Department of Defense has funded a $28 million landmark trial at the University of South Florida enrolling 400+ veterans to evaluate HBOT for TBI and PTSD.

Stroke Recovery

Efrati and colleagues’ 2013 study in PLoS ONE demonstrated significant neurological improvements in 74 patients who were 6 to 36 months post-stroke, with SPECT imaging documenting increased brain metabolic activity. A 2020 follow-up by Hadanny and colleagues extended these findings to patients more than 3 years post-stroke.

Anti-Aging and Telomere Lengthening

Published by Efrati and colleagues in the journal Aging, this prospective trial enrolled 35 healthy adults over age 64 who underwent 60 daily HBOT sessions at 2.0 ATA.⁷ Telomere length in peripheral blood mononuclear cells increased by 20-38% depending on cell type. Senescent cell populations decreased by approximately 37.3%.

60 HBOT sessions at 2.0 ATA resulted in telomere lengthening of more than 20% in immune cells and a 37.3% decrease in senescent T cells. These changes occurred without any lifestyle, diet, or medication changes.”
Efrati et al. 2020, Aging (35 participants over age 64)

Important caveats: sample size was 35 participants, no control group, and long-term significance of telomere changes for actual health outcomes is unknown. Larger controlled trials are needed. Explore this further on our hyperbaric chamber anti-aging page.

Stem Cell Mobilization

Thom and colleagues’ 2006 study in the American Journal of Physiology demonstrated that a single HBOT session at 2.0 ATA doubled circulating stem progenitor cells (CD34+ cells) in human subjects.⁸ After 20 sessions, circulating stem cell levels increased by approximately 800% compared to baseline.

3. Moderate Evidence: Conditions With Promising but Limited Data

Fibromyalgia

Efrati et al. (2015) published a prospective crossover trial showing HBOT significantly improved pain thresholds, symptom questionnaires, and quality of life in fibromyalgia patients.⁹ Brain SPECT imaging showed objective changes in pain-processing regions. This remains a single-center study requiring replication.

Long COVID

The Tel Aviv RCT enrolled 73 patients with post-COVID cognitive symptoms and demonstrated significant improvements in neuropsychological testing across attention, executive function, and memory, along with increased brain perfusion on MRI.¹⁰ A 2023 multicenter registry study tracked 149 Long COVID patients receiving HBOT and found Neurobehavioral Symptom Inventory scores dropped from 30.6 to 14.4 (P<0.001).¹¹

Inflammatory Bowel Disease

A 2023 meta-analysis of 164 IBD patients receiving 5,125 HBOT sessions found 87% overall clinical response in fistulizing Crohn’s disease (95% CI 0.70-0.95) with 59% complete remission.¹² Ulcerative colitis showed 87% clinical remission in a separate analysis.

Fertility

A 2025 study found that 4-7 HBOT sessions in patients with poor ovarian reserve improved oocyte number, follicle output rate, and embryo quality. Before HBOT, 58.54% of treatment cycles produced no available embryos; after HBOT, this dropped to 14.63% (P<0.001).¹³

4. Understanding HBOT Research: Pressure and Protocol

One of the most common mistakes in evaluating HBOT research is not accounting for treatment pressure:

• 1.3 ATA (soft chambers): FDA-cleared only for altitude sickness. Not considered medical-grade HBOT. Insufficient to significantly increase tissue oxygenation for most clinical indications.
• 2.0 ATA: The most common pressure in clinical trials. Used in the telomere, fibromyalgia, stroke, and Long COVID studies. Increases blood oxygen approximately 10-fold above normal.
• 2.4-3.0 ATA: Used primarily for emergency indications. Higher oxygen toxicity risk at these pressures, so treatment durations are shorter.

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

5. Common Study Limitations

• Small sample sizes: Most HBOT trials enroll 30-100 participants. Few exceed 200.
• Short follow-up: Many studies measure outcomes immediately after the protocol ends. Long-term durability is often unknown.
• Single-center studies: Much of the most exciting research comes from one or two groups, notably Efrati’s team at Tel Aviv University. Independent replication is essential but often lacking.
• Heterogeneous protocols: Studies vary in pressure (1.3-3.0 ATA), session count (10-60), and duration (60-120 minutes), making direct comparisons difficult.
• Funding limitations: HBOT cannot be patented, so pharmaceutical companies have no financial incentive to fund large trials.

What to Watch: Ongoing Trials

• HOT-TBI (multi-center RCT): A large Department of Defense trial examining HBOT for mild TBI with improved sham design
• Long COVID multi-center trials: Groups in the US, Israel, and UK running randomized trials following the positive Zilberman-Itskovich results¹⁰
• Aging and cognitive decline: The Tel Aviv group expanding their telomere work to larger cohorts with longer follow-up⁷
• USF TBI trial: $28 million, 400+ veterans, examining HBOT for TBI and PTSD

How to Read an HBOT Study

Study design hierarchy, from strongest to weakest: systematic reviews and meta-analyses, RCTs, observational studies, case series. Key questions to ask: How many patients? Was there a control group? Was it sham-controlled? What pressure was used? When you see claims like “HBOT is proven to treat X,” check whether the supporting study was an RCT with 50+ patients, or a case series of 8 people at a clinic that sells HBOT sessions.