Hyperbaric Oxygen Therapy (HBOT): Pressure as Medicine
Henry's Law: the amount of gas dissolved in a liquid is directly proportional to the pressure of that gas above the liquid. Breathe 100% oxygen at sea level, and your plasma carries a modest amount of dissolved O2 — most oxygen rides hemoglobin.
Hyperbaric Oxygen Therapy (HBOT): Pressure as Medicine
The Simple Principle Behind Profound Healing
Henry’s Law: the amount of gas dissolved in a liquid is directly proportional to the pressure of that gas above the liquid. Breathe 100% oxygen at sea level, and your plasma carries a modest amount of dissolved O2 — most oxygen rides hemoglobin. Now increase the pressure to 2.0 atmospheres absolute (ATA), and plasma oxygen levels jump 10 to 15 times above normal. Oxygen floods into tissues independent of hemoglobin, reaching areas with compromised blood supply that red blood cells cannot access — ischemic wound beds, swollen brain tissue, radiation-damaged capillary fields.
This is not theory. It is gas physics applied to healing. And the downstream biological effects extend far beyond simple oxygen delivery.
Physiological Mechanisms
Hyperoxia Effects: At 2.0 ATA breathing 100% O2, arterial pO2 reaches approximately 1,400 mmHg (normal sea level: ~100 mmHg). This hyperoxygenation drives several cascades:
Angiogenesis: Sustained hyperoxia followed by return to normoxia creates a cyclic oxygen gradient that is the strongest natural stimulus for new blood vessel formation. VEGF (vascular endothelial growth factor) and other angiogenic factors increase. Over a series of treatments, new capillary beds grow into previously ischemic tissue. This is why HBOT requires 20-40+ sessions — you are literally growing new vasculature.
Stem Cell Mobilization: Thom 2006 (University of Pennsylvania) demonstrated that a single HBOT session at 2.0 ATA doubled circulating stem cells (CD34+). After 20 sessions, circulating stem cell counts increased 800%. These mobilized stem cells home to damaged tissue and participate in repair. This finding was paradigm-shifting — HBOT as a stem cell therapy without injections.
Anti-Inflammatory: Hyperbaric oxygen downregulates NF-kB, reduces TNF-alpha, IL-1, and IL-6 production, and decreases leukocyte adhesion to endothelium (reducing inflammatory tissue damage). For conditions driven by chronic inflammation — TBI, autoimmune disease, post-COVID — this mechanism is central.
Antimicrobial: Oxygen-dependent killing by neutrophils requires tissue pO2 above 30-40 mmHg. In ischemic infected wounds, tissue pO2 may be below 10 mmHg — neutrophils are present but cannot kill. HBOT restores the oxygen tension needed for the oxidative burst. Additionally, high oxygen tensions are directly toxic to anaerobic bacteria (gas gangrene, necrotizing infections).
Edema Reduction: Hyperoxic vasoconstriction reduces blood flow to swollen areas (seemingly paradoxical), but the increased dissolved oxygen more than compensates — net oxygen delivery increases while edema fluid is reduced. Critical for traumatic brain injury and crush injuries.
Collagen Synthesis: Prolyl hydroxylase and lysyl hydroxylase — the enzymes that crosslink collagen — are oxygen-dependent. Without adequate tissue oxygen, collagen cannot properly form. HBOT provides the oxygen substrate for wound matrix construction.
Neuroplasticity: SPECT imaging studies by Paul Harch MD (2012) demonstrated improved cerebral blood flow patterns after HBOT in TBI patients. The combination of angiogenesis, stem cell mobilization, inflammation reduction, and direct metabolic support to neurons creates conditions for neuroplastic recovery even years after initial injury.
Pressure Protocols
Mild Hyperbaric (mHBOT): 1.3-1.5 ATA
Soft-sided inflatable chambers that pressurize to 1.3-1.5 ATA using room air or concentrated oxygen (not 100% O2 — oxygen concentrators deliver 90-95%). Home use possible with physician oversight.
Advantages: Accessible, affordable ($3,000-15,000 for chamber purchase), safe (lower pressure = lower risk), daily use feasible, no prescription required in some jurisdictions for 1.3 ATA units.
Limitations: Lower oxygen tension means less potent effects per session. Requires more sessions and longer treatment courses. Not sufficient for serious decompression illness or acute conditions.
Best for: Mild TBI and concussion (significant evidence at 1.3-1.5 ATA), chronic inflammation, general brain health, anti-aging wellness, mild cognitive decline, athletic recovery, chronic fatigue, children with neurodevelopmental conditions.
Standard Clinical: 1.5-2.4 ATA
Hard-sided monoplace (single person) or multiplace (room-sized) chambers. Medical facility setting. 100% oxygen delivered via mask or hood. This is where the bulk of clinical evidence exists.
Monoplace chambers: Patient lies in a clear acrylic cylinder, entire chamber pressurized with O2. Simpler, less expensive, most common in outpatient clinics. Cannot easily access patient during treatment.
Multiplace chambers: Room-sized, pressurized with air, patients breathe 100% O2 via mask or hood. Allows attendants inside, direct patient access, treatment of critically ill or ventilated patients. Hospital-based.
Protocols by condition:
- TBI/concussion: 1.5-2.0 ATA, 60 minutes, 40-60 sessions
- Wound healing: 2.0-2.4 ATA, 90 minutes, 20-40 sessions
- Radiation injury: 2.0-2.4 ATA, 90 minutes, 40-60 sessions
- Post-stroke: 1.5-2.0 ATA, 60-90 minutes, 40-60 sessions
High-Pressure: 2.4-3.0 ATA
Hospital-based, typically multiplace chambers. Reserved for emergencies and specific indications where maximum oxygen delivery is critical.
Indications: Decompression sickness (the bends — divers), arterial gas embolism, carbon monoxide poisoning (acute — must treat within 6-12 hours for maximum benefit), gas gangrene.
FDA-Approved Indications (13 Conditions)
The FDA has cleared HBOT for thirteen specific diagnoses. Insurance coverage generally applies only to these:
- Air or gas embolism
- Carbon monoxide poisoning
- Gas gangrene (clostridial myonecrosis)
- Crush injury, compartment syndrome
- Decompression sickness
- Non-healing diabetic wounds (Wagner grade 3+)
- Exceptional blood loss anemia (when transfusion unavailable)
- Intracranial abscess
- Necrotizing soft tissue infections
- Chronic refractory osteomyelitis
- Delayed radiation injury (osteoradionecrosis, soft tissue radionecrosis)
- Compromised skin grafts and flaps
- Acute thermal burns
For diabetic wounds alone, HBOT has a number needed to treat (NNT) of 3-4 to prevent one amputation — among the strongest NNTs in all of medicine.
Off-Label and Emerging Applications
The real frontier of HBOT lies beyond the FDA’s thirteen. Here, the evidence is growing through clinical trials, case series, and an explosion of research from Israeli hyperbaric centers under Shai Efrati MD at the Sagol Center for Hyperbaric Medicine and Research.
Traumatic Brain Injury and Concussion
The most compelling emerging indication. TBI creates a penumbra of injured-but-not-dead neurons — cells in metabolic crisis that need oxygen and reduced inflammation to recover.
Key studies:
- Boussi-Gross 2013: 56 post-concussion patients (1-5 years post-injury) received 40 sessions at 1.5 ATA. Significant improvements in cognitive function, quality of life, and SPECT perfusion imaging. Control group showed no change.
- Hadanny 2022: Randomized controlled trial — 60 sessions at 2.0 ATA improved cognitive function, brain MRI microstructural changes, and cerebral blood flow in mild TBI patients years after injury.
- Harch 2012: Case series showing dramatic SPECT improvements and clinical recovery in blast-related TBI in military veterans.
Protocol: 40-60 sessions at 1.5-2.0 ATA, 60 minutes, 5 days per week. Improvements often progressive — patients continue to improve for months after completing the treatment course.
Stroke Recovery
Efrati 2013: Randomized controlled trial of post-stroke patients (6 months to 3 years post-stroke) receiving 40 HBOT sessions at 2.0 ATA. Significant neurological improvement in motor function, language, and daily living activities — even years after the stroke. SPECT imaging showed new metabolic activity in previously dormant brain regions. The concept of a “therapeutic window” for stroke recovery may be much wider than previously believed.
Long COVID and Post-COVID Syndrome
Zilberman-Itskovich 2022 (randomized, double-blind, sham-controlled): 73 long COVID patients received 40 sessions at 2.0 ATA. Significant improvements in fatigue, brain fog (cognitive function), executive function, energy, sleep, and psychiatric symptoms compared to sham. Brain MRI showed microstructural improvements.
The mechanisms align perfectly with long COVID pathophysiology: improved tissue oxygenation (microclot-induced ischemia), reduced neuroinflammation, enhanced mitochondrial function, and stem cell mobilization for tissue repair.
Anti-Aging: The Telomere Study
Hadanny 2020 (Tel Aviv University): 35 healthy adults over 64 received 60 HBOT sessions at 2.0 ATA in a unique protocol with air breaks (intermittent hyperoxia). Results:
- Telomere length INCREASED by 20% in B-cells and 37.5% in T-helper cells
- Senescent cell population DECREASED by 37% in T-helper cells
This was the first intervention in human history demonstrated to lengthen telomeres and clear senescent cells — the two hallmarks of biological aging. The intermittent hyperoxia-normoxia cycling was key (hormetic stress, not constant exposure).
Autism Spectrum
Rossignol 2009: Double-blind, controlled trial — 62 children with autism received 40 sessions at 1.3 ATA with 24% oxygen. Significant improvements in overall functioning, receptive language, social interaction, eye contact, and sensory/cognitive awareness versus control group. Mechanism: reduction of neuroinflammation, improved cerebral perfusion to hypoperfused brain regions.
Cancer Adjunctive
The old myth that HBOT “feeds cancer” because tumors love oxygen has been thoroughly debunked. Moen 2012 conducted a systematic review and found no evidence that HBOT promotes cancer growth or recurrence. In fact, hypoxic tumors are more aggressive, more resistant to radiation and chemotherapy, and more likely to metastasize.
HBOT as cancer adjunctive: enhances radiation therapy effectiveness (oxygen-dependent free radical damage to DNA), may improve chemotherapy delivery to hypoxic tumor regions, reduces radiation side effects (especially for pelvic and head/neck radiation), supports immune surveillance.
Additional Emerging Applications
- Chronic Lyme disease: Reduces biofilm (hyperbaric oxygen penetrates biofilm matrices), enhances antibiotic efficacy (many antibiotics are oxygen-dependent), immune support, neurological recovery
- ME/CFS and fibromyalgia: Israeli studies show improved symptoms, brain SPECT changes, quality of life
- Sports recovery: Professional teams and elite athletes use HBOT for faster injury recovery, reduced inflammation, enhanced performance recovery
- Cosmetic/anti-aging: Improved skin quality, collagen synthesis, cellular rejuvenation (the Tel Aviv telomere findings spurred enormous commercial interest)
Treatment Experience
A typical session: The patient enters the chamber (monoplace — lies down on a padded stretcher that slides into the clear acrylic tube; multiplace — sits in a chair inside a room). The chamber pressurizes over 10-15 minutes. During pressurization, the patient must equalize ear pressure — swallowing, jaw movement, or Valsalva maneuver (like during airplane descent or scuba diving). At treatment pressure, the patient simply breathes and rests for 60-90 minutes. Many patients read, sleep, or watch content on a tablet. Depressurization takes 10-15 minutes.
Sessions are usually daily, 5 days per week, for 4-12 weeks depending on the condition. The cumulative effect matters — the angiogenesis, stem cell mobilization, and neuroplastic changes build over sessions. A single session provides temporary oxygen boost; a full course creates lasting structural change.
Side Effects and Risks
Common (mild):
- Ear and sinus barotrauma: The most frequent side effect. Equalization techniques prevent most cases. Patients with eustachian tube dysfunction may need myringotomy tubes for prolonged courses.
- Temporary myopia: High-pressure oxygen causes reversible lens changes. Vision typically returns to baseline within 2-8 weeks after completing treatment.
- Fatigue: Some patients feel tired after sessions, especially early in the course (healing consumes energy).
Rare:
- Oxygen toxicity seizure: Extremely rare at clinical pressures (1 in 10,000 treatments at 2.0 ATA). Self-limiting — remove the oxygen, the seizure stops. No permanent injury. Risk increases above 2.4 ATA and with longer treatment times.
- Claustrophobia: Monoplace chambers can trigger claustrophobia. Mild sedation, coaching, and gradual exposure help. Multiplace chambers are better for claustrophobic patients.
- Pulmonary oxygen toxicity: Only with prolonged daily high-pressure exposure (military diving scenarios). Not relevant to standard clinical protocols with air breaks.
Contraindications:
- Untreated pneumothorax (absolute — air expansion under pressure is dangerous)
- Certain chemotherapy agents: Bleomycin (pulmonary toxicity potentiation), cisplatin (possible interaction). Timing matters — discuss with oncologist.
- Severe COPD with CO2 retention (hypoxic drive — high-flow O2 can suppress respiratory drive)
- Unstable seizure disorder (relative — lower threshold for oxygen toxicity seizure)
- Active upper respiratory infection or severe sinus congestion (barotrauma risk)
- Pregnancy (insufficient safety data — precautionary)
Cost and Access
The economic reality of HBOT varies dramatically:
- Insurance-covered (FDA-approved indications): Typically $150-300 per session after copay
- Out-of-pocket (off-label): $100-300 per session, $4,000-18,000 for a full 40-60 session course
- Home mild chambers (1.3 ATA): $3,000-15,000 purchase price. Daily home use makes long-term protocols feasible.
- Freestanding HBOT clinics: Growing nationally and internationally, making access easier than hospital-based programs
For the functional medicine patient with TBI, long COVID, or chronic infection, HBOT represents a significant financial commitment. But the evidence for conditions like mild TBI — where few other interventions show comparable efficacy — often justifies the investment. The Israeli studies continue to expand the evidence base, and as data grows, insurance coverage for additional indications may follow.
The chamber is a vessel. Pressure is the lever. Oxygen is the medicine. And the body, given what it needs, does the healing itself.