Hyperbaric Oxygen Therapy: Benefits, Evidence, and What to Expect

What Is Hyperbaric Oxygen Therapy?

Hyperbaric oxygen therapy (HBOT) involves breathing pure or concentrated oxygen inside a pressurized chamber. The word “hyperbaric” simply means “higher than normal pressure.” During a session, the atmospheric pressure inside the chamber is raised to 1.3-3.0 times normal sea-level pressure, and you breathe close to 100% oxygen for a set period, typically 60-90 minutes [1].

The concept isn’t new. Compressed air therapy dates back to the 1600s, and physicians began using pressurized oxygen for decompression sickness in the early 1900s. What has changed is the breadth of clinical applications. Over the past two decades, research into HBOT has expanded well beyond diving medicine into wound care, neurology, immunology, and sports performance [2].

How Pressurized Oxygen Works: Henry’s Law in Action

Under normal conditions, nearly all the oxygen in your blood is bound to hemoglobin inside red blood cells. Hemoglobin is already about 97% saturated at sea level, so simply breathing more oxygen at normal pressure doesn’t increase delivery much. This is where pressure changes the equation.

Henry’s law states that the amount of gas dissolved in a liquid is directly proportional to the pressure of that gas above the liquid. When you increase atmospheric pressure inside a hyperbaric chamber, oxygen dissolves directly into your blood plasma, cerebrospinal fluid, lymph, and interstitial fluids, bypassing hemoglobin entirely [3].

At 2.0 ATA breathing 100% oxygen, the dissolved oxygen in plasma increases roughly 10-fold. At 3.0 ATA, it can increase 15-fold or more. This dissolved oxygen can reach areas with compromised blood flow, swollen tissues, or damaged capillaries where red blood cells simply cannot go [3].

This mechanism produces several downstream effects:

• Angiogenesis: the growth of new blood vessels into hypoxic tissue [4]
• Reduced edema through vasoconstriction that paradoxically still increases oxygen delivery
• Enhanced white blood cell function, improving the body’s ability to fight infection [5]
• Upregulation of stem cell mobilization from bone marrow [6]
• Reduced inflammatory cytokines and suppression of NF-kB signaling [7]

FDA-Approved Conditions

The FDA and Undersea and Hyperbaric Medical Society (UHMS) currently recognize 14 indications for HBOT [8]:

• Air or gas embolism
• Carbon monoxide poisoning
• Gas gangrene (clostridial myositis and myonecrosis)
• Crush injuries, compartment syndrome, and acute traumatic ischemia
• Decompression sickness (the bends)
• Arterial insufficiency (central retinal artery occlusion)
• Severe anemia when transfusion is not possible
• Intracranial abscess
• Necrotizing soft tissue infections
• Refractory osteomyelitis
• Delayed radiation injury (soft tissue and bone)
• Compromised skin grafts and flaps
• Thermal burn injuries
• Diabetic foot ulcers and other non-healing wounds

Of these, wound healing is by far the most common clinical application. Chronic non-healing wounds affect roughly 6.5 million Americans, and HBOT has become a standard adjunctive therapy in many wound care centers across the country [9].

Off-Label Uses With Growing Evidence

Traumatic Brain Injury and Concussion

HBOT for brain injury is one of the most actively researched off-label applications. The rationale is straightforward: brain tissue damaged by trauma develops chronic hypoxia and neuroinflammation that persists long after the initial injury. By flooding these oxygen-starved regions with dissolved oxygen, HBOT can reactivate stunned neurons and stimulate repair mechanisms [10].

A landmark 2013 study by Boussi-Gross and colleagues showed that HBOT (1.5 ATA, 60 sessions) produced significant improvements in cognitive function and quality of life in patients with mild TBI, even years after the initial injury. Brain SPECT imaging confirmed increased activity in previously hypoperfused regions [10].

Military research has also been promising. A study of U.S. service members with combat-related TBI found that 40 sessions at 2.0 ATA produced measurable improvements in post-concussive symptoms, PTSD scores, and cognitive testing compared to sham controls [11].

Stroke Recovery

Stroke leaves behind a region of tissue called the ischemic penumbra, where neurons are metabolically impaired but not dead. HBOT research suggests that these cells can be reactivated. A 2013 randomized controlled trial demonstrated that HBOT improved neurological function in post-stroke patients even 6-36 months after the event, well outside the traditional window for stroke recovery [12].

Long COVID

One of the more recent applications involves long COVID, particularly cognitive symptoms, fatigue, and exercise intolerance. A 2022 randomized, double-blind, sham-controlled trial from Israel found that 40 sessions of HBOT (2.0 ATA) significantly improved cognitive function, energy levels, sleep quality, and psychiatric symptoms in long COVID patients. Brain MRI showed increased perfusion in regions associated with the reported improvements [13].

The proposed mechanism involves reversing endothelial dysfunction and microclot formation, both of which contribute to tissue hypoxia in long COVID.

Sports Recovery and Performance

Professional athletes have used HBOT for years to accelerate recovery from soft tissue injuries, fractures, and post-surgical healing. The evidence here is less robust than in wound care or TBI, but several controlled studies support the logic.

A 2011 study in the Journal of Science and Medicine in Sport found that HBOT accelerated recovery from muscle injuries in professional rugby players, reducing time to return to play [14]. The mechanisms, enhanced oxygen delivery, reduced edema, accelerated collagen synthesis, apply directly to athletic injuries.

Anti-Aging and Telomere Biology

A widely cited 2020 study by Hachmo et al. found that a specific HBOT protocol (60 sessions at 2.0 ATA with intermittent hypoxic exposure) significantly lengthened telomeres and decreased senescent cell populations in healthy adults over 64 years old. Telomeres lengthened by over 20% in some immune cell populations, a finding with no pharmaceutical equivalent at the time of publication [15].

What a Session Looks Like

If you’ve never been inside a hyperbaric chamber, here’s what to expect.

You’ll arrive at the clinic wearing comfortable, 100% cotton clothing. No electronics, lighters, hair products, or petroleum-based lotions are allowed inside the chamber because of the elevated oxygen environment. The technician or attending physician will review your medical history and check your ears for any conditions that might impair pressure equalization.

There are two main types of chambers:

Monoplace (Single-Person) Chambers

These are clear acrylic tubes that fit one person. You lie down, and the entire chamber is pressurized with oxygen. Most hospital-based wound care programs use monoplace chambers at pressures between 2.0 and 2.4 ATA.

Multiplace Chambers

These are large, room-like chambers that can accommodate multiple patients plus a technician. Patients breathe oxygen through a hood or mask while the chamber is pressurized with compressed air. Military and research facilities often use multiplace chambers.

Mild Hyperbaric Chambers (Soft Chambers)

Portable, inflatable chambers that operate at lower pressures, typically 1.3-1.5 ATA. These are often used in clinics and home settings. They cannot reach the pressures of medical-grade hard chambers, and they typically use oxygen concentrators rather than 100% oxygen, so the effective oxygen delivery is lower. There is debate within the HBOT community about whether mild chambers produce clinically meaningful results for conditions beyond basic wellness, though some research at 1.3 ATA has shown benefits for concussion and mild TBI [16].

During the Session

The session begins with a “descent” phase lasting 5-10 minutes as pressure gradually increases. You may feel fullness or pressure in your ears, similar to flying or scuba diving. Techniques like swallowing, yawning, or the Valsalva maneuver (gently blowing against pinched nostrils) help equalize the pressure.

Once at treatment pressure, you simply rest. Many patients read, listen to audiobooks, or sleep. The treatment phase lasts 60-90 minutes, depending on the protocol. Finally, the chamber gradually depressurizes over 5-10 minutes during “ascent.”

Most people describe the experience as relaxing. The most common sensation is warmth during pressurization and slight cooling during depressurization.

Protocols: How Many Sessions Do You Need?

This depends entirely on the condition being treated:

• Wound healing: 20-40 sessions at 2.0-2.4 ATA, typically 5 days per week [9]
• TBI/concussion: 40-60 sessions at 1.5-2.0 ATA, 5 days per week [10]
• Long COVID: 40 sessions at 2.0 ATA, 5 days per week [13]
• Sports recovery: 10-20 sessions at 1.5-2.0 ATA, or acute sessions post-injury
• General wellness/anti-aging: 40-60 sessions at 2.0 ATA for the telomere protocol [15], with ongoing maintenance sessions varying by provider

Some conditions show improvement within 10-15 sessions. Others, particularly neurological conditions, often require 40 sessions or more before significant changes become apparent. Brain tissue remodeling is a slow process, and premature discontinuation is one of the most common reasons patients don’t see results.

Risks and Side Effects

HBOT has a strong safety profile when administered by trained operators within established protocols. However, no therapy is without risks.

Common side effects:

• Middle ear barotrauma (ear pressure or pain), the most frequent complaint, occurring in up to 2% of patients [17]
• Sinus pressure or congestion
• Temporary nearsightedness (myopic shift), which resolves after completing treatment
• Mild fatigue after sessions, particularly early in a treatment course

Rare but serious risks:

• Oxygen toxicity seizures, extremely rare at clinical pressures (roughly 1 in 10,000 sessions) [17]
• Pulmonary barotrauma (lung injury from pressure), almost exclusively seen in patients with untreated air trapping conditions like bullous emphysema
• Claustrophobia in monoplace chambers, manageable with mild anxiolytics or the use of multiplace chambers

Contraindications include:

• Untreated pneumothorax (collapsed lung)
• Certain chemotherapy agents (some, like doxorubicin, may interact with high-oxygen environments)
• Uncontrolled high fevers
• Severe congestive heart failure

How to Choose a Provider

Not all HBOT facilities are equal. When evaluating a provider, consider:

• Medical oversight: Is there a physician trained in hyperbaric medicine on staff? Look for board certification through the UHMS or the American Board of Emergency Medicine with added qualifications in undersea and hyperbaric medicine.
• Chamber type: For FDA-approved indications and most off-label neurological protocols, you need a hard-shell chamber capable of reaching at least 2.0 ATA.
• Protocol knowledge: Ask about the specific pressure, duration, and number of sessions they recommend for your condition. Providers should be able to cite the research behind their protocol choices.
• Safety systems: The facility should have fire suppression systems, continuous monitoring, and emergency depressurization capabilities.

The Bottom Line

HBOT is one of the few therapies with both a long clinical track record and an expanding evidence base across diverse conditions. For FDA-approved indications like wound healing and carbon monoxide poisoning, the evidence is robust and insurance typically covers treatment. For off-label applications like TBI, stroke, and long COVID, the research is increasingly compelling but not yet reflected in insurance coverage at most providers.

The mechanism is elegant in its simplicity: deliver more oxygen to tissues that need it, and the body’s own repair systems can do what they were designed to do. That principle applies whether you’re healing a diabetic foot ulcer or recovering from a brain injury.

References

[1] Ortega MA, Fraile-Martinez O, García-Montero C, et al. A general overview on the hyperbaric oxygen therapy: applications, mechanisms and translational opportunities. Medicina (Kaunas). 2021;57(9):864. doi:10.3390/medicina57090864. PMID: 34577787

[2] Undersea and Hyperbaric Medical Society. Indications for hyperbaric oxygen therapy. UHMS Guidelines. 14th ed. 2019.

[3] Gill AL, Bell CN. Hyperbaric oxygen: its uses, mechanisms of action and outcomes. QJM. 2004;97(7):385-395. doi:10.1093/qjmed/hch074. PMID: 15208426

[4] Thom SR. Hyperbaric oxygen: its mechanisms and efficacy. Plast Reconstr Surg. 2011;127 Suppl 1(Suppl 1):131S-141S. doi:10.1097/PRS.0b013e3181fbe2bf. PMID: 21200283

[5] Knighton DR, Halliday B, Hunt TK. Oxygen as an antibiotic: the effect of inspired oxygen on infection. Arch Surg. 1984;119(2):199-204. doi:10.1001/archsurg.1984.01390140057010. PMID: 6696611

[6] Thom SR, Bhopale VM, Velazquez OC, Goldstein LJ, Thom LH, Buerk DG. Stem cell mobilization by hyperbaric oxygen. Am J Physiol Heart Circ Physiol. 2006;290(4):H1378-H1386. doi:10.1152/ajpheart.00888.2005. PMID: 16299259

[7] Benson RM, Minter LM, Osborne BA, Granowitz EV. Hyperbaric oxygen inhibits stimulus-induced proinflammatory cytokine synthesis by human blood-derived monocyte-macrophages. Clin Exp Immunol. 2003;134(1):57-62. doi:10.1046/j.1365-2249.2003.02248.x. PMID: 12974755

[8] Moon RE, ed. Hyperbaric Oxygen Therapy Indications. 14th ed. North Palm Beach, FL: Undersea and Hyperbaric Medical Society; 2019.

[9] Kranke P, Bennett MH, Martyn-St James M, Schnabel A, Debus SE, Weibel S. Hyperbaric oxygen therapy for chronic wounds. Cochrane Database Syst Rev. 2015;(6):CD004123. doi:10.1002/14651858.CD004123.pub4. PMID: 26106870

[10] Boussi-Gross R, Golan H, Fishlev G, et al. Hyperbaric oxygen therapy can improve post concussion syndrome years after mild traumatic brain injury: randomized prospective trial. PLoS One. 2013;8(11):e79995. doi:10.1371/journal.pone.0079995. PMID: 24260334

[11] Harch PG, Andrews SR, Fogarty EF, et al. A phase I study of low-pressure hyperbaric oxygen therapy for blast-induced post-concussion syndrome and post-traumatic stress disorder. J Neurotrauma. 2012;29(1):168-185. doi:10.1089/neu.2011.1895. PMID: 22026588

[12] Efrati S, Fishlev G, Bechor Y, et al. Hyperbaric oxygen induces late neuroplasticity in post stroke patients: randomized, prospective trial. PLoS One. 2013;8(1):e53716. doi:10.1371/journal.pone.0053716. PMID: 23335971

[13] Zilberman-Itskovich S, Catalogna M, Sasson E, et al. Hyperbaric oxygen therapy improves neurocognitive functions and symptoms of post-COVID condition: randomized controlled trial. Sci Rep. 2022;12(1):11252. doi:10.1038/s41598-022-15565-0. PMID: 35821512

[14] Babul S, Rhodes EC. The role of hyperbaric oxygen therapy in sports medicine. Sports Med. 2000;30(6):395-403. doi:10.2165/00007256-200030060-00002. PMID: 11132122

[15] Hachmo Y, Hadanny A, Abu Hamed R, et al. Hyperbaric oxygen therapy increases telomere length and decreases immunosenescence in isolated blood cells: a prospective trial. Aging (Albany NY). 2020;12(22):22445-22456. doi:10.18632/aging.202188. PMID: 33206062

[16] Mozayeni BR, Duncan W, Zant E, Love TL, Beckman RL, Stoller KP. The National Brain Injury Rescue and Rehabilitation Project: a preliminary report on the hyperbaric oxygen treatment of mild traumatic brain injury. Med Gas Res. 2019;9(1):1-7. doi:10.4103/2045-9912.254636. PMID: 30950413

[17] Plafki C, Peters P, Almeling M, Welslau W, Busch R. Complications and side effects of hyperbaric oxygen therapy. Aviat Space Environ Med. 2000;71(2):119-124. PMID: 10685584

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