Oxygen is essential for life. Hyperbaric oxygen therapy, or HBOT, is a form of therapy that delivers 100% oxygen to the body at high pressures. Read on to learn about the approved and off-label uses of HBOT and when it can be dangerous.
What is Oxygen Therapy?
Oxygen therapy is the use of supplemental oxygen to treat a variety of medical conditions. There are two main types of oxygen therapies available:
- Normobaric oxygen therapy
- Hyperbaric oxygen therapy
Normobaric oxygen therapy is supplemental oxygen administered at the same pressure of our atmosphere (1 atm). Depending on the medical condition, 40 to 100% of saturated oxygen is delivered to the body.
As excessive oxygen can be harmful, normobaric oxygen therapy should be carefully supervised by a doctor. In the absence of correct medical supervision, normobaric oxygen therapy can also cause heart disease, inflammation, diabetes, and aging [1].
Hyperbaric oxygen therapy is 100% saturated supplemental oxygen delivered at higher atmospheric pressures. Patients are placed in a high pressure, full body chamber (hyperbaric chamber). This increases oxygen delivery to all of the tissues of the body [2].
Treatment schedules of hyperbaric oxygen therapy vary between 60 to 120 minutes, 1 or more times daily [2].
Hyperbaric oxygen therapy is approved for the treatment of a number of conditions such as air or gas embolisms, burns, diabetic wounds, and traumatic ischemia.
Mechanism
Blood is made up of 4 components: Plasma, red blood cells, white blood cells, and platelets. Oxygen is transported through red blood cells that contain the protein hemoglobin. Hemoglobin is an iron-containing protein that oxygen can bind to [3].
The only differences between normobaric and hyperbaric oxygen therapy are the pressure that they’re applied at and the method of delivery. Both forms of therapy increase the amount of oxygen that is delivered in the blood [4].
With hyperbaric oxygen therapy, there is a 10 to 20 fold increase in blood plasma oxygen. It also induces an increase in red blood cells [5].
In clinical and animal studies, hyperbaric oxygen therapy promoted [6]:
- Cell growth
- Reduction of swelling
- New blood vessel formation
- Tissue repair
- Wound healing
Hyperbaric oxygen therapy causes the controlled release of reactive oxygen species (ROS) in damaged and infected tissues [7].
The enhanced healing action of hyperbaric oxygen therapy is due to its direct antifungal activity mediated by reversal of fungal growth and restoration of a protective immune response [8].
Health Benefits
Hyperbaric oxygen therapy is a potentially lifesaving medical procedure that should only be conducted by a medical professional. If you suspect that you have any of the following conditions, seek medical attention immediately.
Approved Uses of HBOT
1) Decompression Illness
Scuba diving with a compressed air supply can cause decompression sickness and arterial gas embolism, a potentially lethal event [9].
Decompression sickness is caused by the formation of nitrogen bubbles in the blood and tissues of scuba divers who surface too quickly [10].
Arterial gas embolisms happen after decompression sickness. The gas bubbles in the bloodstream and tissues travel within the blood and block the supply of blood to the lungs (pulmonary vein) [10].
According to the US Navy 6 treatment manual, hyperbaric oxygen therapy is the preferred way to treat decompression sickness [11].
Hyperbaric oxygen therapy is most successful in treating decompression illness within 24 hours of surfacing [9].
In a clinical case report, a single session of emergency hyperbaric oxygen therapy removed the gas and air bubbles in the patient’s blood vessels, hip, lower spine, brain sinuses, and joints [12].
Hyperbaric oxygen therapy also protected rats from spinal cord injury during simulated diving [13].
In rabbits, hyperbaric oxygen therapy reduced lung injury caused by decompression sickness [14].
2) Air Embolism
Air embolism is caused by the introduction of air bubbles into the bloodstream which blocks arteries.
Air embolism is a rare but potentially fatal complication of surgical procedures and causes serious damage to the brain, heart, and lungs [15].
Clinical symptoms of an air embolism depend on the location of the air bubble or bubbles in the body. Early treatment is critical for survival [15].
A clinical case study of a patient suffering from an air embolism after open heart surgery showed complete recovery after 7 sessions of hyperbaric oxygen therapy [16].
A clinical case study of an immunocompromised patient with air embolism showed that emergency hyperbaric oxygen therapy cured brain (ischemic) stroke symptoms caused by an invasive fungal infection [17].
3) Carbon Monoxide Poisoning
Carbon monoxide can displace oxygen in the blood. This reduces the amount of oxygen supplied to tissues.
In a population-based study of 7,287 patients suffering from carbon monoxide poisoning, hyperbaric oxygen therapy reduced the death rate and improved patient lifespan. Therapy was more effective in younger patients (<20) and patients with acute lung failure [18].
In rats with acute carbon monoxide poisoning, hyperbaric oxygen therapy reduced brain damage and behavior abnormalities [19].
Adjunctive hyperbaric oxygen therapy also protected rats from oxygen toxicity caused by cyanide poisoning [20].
4) Skin Ulcers
In 35 patients with treatment-resistant skin ulcers (vasculitis), a 4-week course of hyperbaric oxygen therapy improved recovery in 80% of the patients [21].
Similarly, in a patient suffering from treatment-resistant skin ulcers, 4 weeks of hyperbaric oxygen therapy promoted complete recovery [22].
In a clinical study, 146 patients treated with supplementary hyperbaric oxygen therapy were found to recover from chronic diabetic foot ulcers [23].
In 2 patients with chronic kidney disease, 20 sessions of hyperbaric oxygen therapy (in addition to standard therapies) completely cured ulcers [24].
A meta-analysis of 9 studies (RCTs) consisting of 526 patients concluded that hyperbaric oxygen therapy is a beneficial therapy for foot ulcers [25].
In a diabetic rat model, hyperbaric oxygen therapy for 6 weeks reduced inflammation, increased blood flow, and improved wound healing [26].
5) Anemia
When applied early, hyperbaric oxygen therapy has a positive effect on severe anemia. It benefits patients who cannot accept blood transfusion for religious reasons, immunologic reasons, or blood availability problems [5].
In a patient suffering from hemorrhage, 10 sessions of hyperbaric oxygen therapy were found to relieve symptoms [27].
6) Brain Abscess
In 40 patients with spontaneous brain abscess (RCT), hyperbaric oxygen therapy administered in addition to antibiotics resulted in the complete recovery for all patients [28].
In 5 children with brain abscesses, hyperbaric oxygen therapy helped promote healing and survival [29].
Hyperbaric oxygen therapy is associated with fewer treatment failures, a decrease in the need for reoperation, and an improved long-term outcome of patients with spontaneous brain abscess [28].
7) Recovery from Radiotherapy
Frequent use of radiation therapy on cancer cells results in injuries of normal tissues surrounding the tumors.
A review of 14 studies with 753 participants (RCTs) concluded that hyperbaric oxygen therapy reduced the radiation injury caused in the head, neck, anus, and rectum [21].
In 57 breast cancer patients, 47 sessions of hyperbaric oxygen therapy decreased tissue toxicity, pain, and oversensitivity of the affected areas [30].
A breast cancer patient with a skin ulcer that developed 25 years after therapy completely recovered after 101 sessions of hyperbaric oxygen therapy [31].
Radiation cystitis is a complication caused by the inflammation of the bladder (cystitis) during radiotherapy of the hip region (pelvic) in patients with urological cancers. In 12 patients with radiation cystitis, hyperbaric oxygen therapy improved symptoms in 67% of the patients [32].
In 21 patients with radiation-induced damage to the upper jaw bone, hyperbaric oxygen therapy cured the majority of the patients (85.7%) [33].
Similarly, 27 patients with radiation-induced damage of the lower jaw bone benefited from supplementing their current treatments with hyperbaric oxygen therapy [34].
In mice, hyperbaric oxygen therapy prevented radiation-induced damage to the lower jaw bone. It also improved the recovery of bone volume and viability [35].
Hyperbaric oxygen therapy prevents the production of proteins that cause fibrosis in mice with head and neck radiation exposure. Fibrosis is a condition caused by the overgrowth of tissue and scarring [36].
Supplementing hyperbaric oxygen therapy for radiation-induced damage to the jawbones should be considered for patients who are not responsive to therapy [37].
8) Burns
Hyperbaric oxygen therapy increases the supply of oxygen to the areas suffering from burns.
Over 800 burn patients treated with hyperbaric oxygen therapy exhibited longer lifespans and shorter recovery times than patients who just used standard therapy [38].
The rate of infections (sepsis) was decreased in 57 burn patients supplemented with hyperbaric oxygen therapy in addition to standard treatment [39].
9) Tissue Graft Acceptance
A tissue graft is a medical procedure in which damaged tissue is replaced using donated healthy tissue. Failure of tissue grafts resulted in tissue loss, additional surgery, increased treatment costs, and unfavorable psychosocial patient effects.
Multiple animals (rats, rabbits, and guinea pigs) and human case studies have shown the success of hyperbaric oxygen therapy in rescuing skin grafts by increasing oxygen supply to the tissues, improving fibroblast function and initiating the growth of new blood vessels [40].
In mice, the addition of hyperbaric oxygen therapy inhibited the immune response and increased the chances of graft acceptance during transplantation [41, 42].
10) Ischemia
Ischemia is a broad category of diseases that results from a lack of oxygen supply to a particular tissue. The best-known ischemic conditions are heart attack (lack of oxygen supply to the heart) and stroke (lack of oxygen supply to the brain).
HBOT is approved for the treatment of acute traumatic ischemias (that is, those caused by a traumatic injury). Some doctors use it to prevent reperfusion injury after a heart attack, and new research suggests that it could help with stroke as well [43, 44].
In 73 post-stroke patients (RCT), 40 sessions of hyperbaric oxygen therapy significantly decreased damage to the brain and nerves [45].
In 12 patients suffering from a stroke after heart surgery, hyperbaric oxygen therapy caused a full recovery in 10 out of the 12 patients [46].
Multiple animal studies with rats have found that hyperbaric oxygen therapy promoted growth and decreased inflammation of the brain tissues. Additionally, it increased oxygen supply and improved oxygen absorption [47, 48, 49, 50].
In rats, adding hyperbaric oxygen therapy to standard therapies suppressed inflammation of the heart tissues and protected against bacterial infection of the inner lining of the heart (endocarditis) [51].
Studies with rat models have found that HBOT protected heart function via antioxidant activity [52].
11) Bone Infections
Osteomyelitis is the infection of bone or bone marrow and is usually caused by bacteria.
A review of 181 patient case reports found that hyperbaric oxygen therapy cured 82.6% of patients with recurrent chronic bone infection [53].
In animal studies, hyperbaric oxygen therapy promoted bone regeneration following injury and surgery [54, 55].
12) Tissue Infections
Bacterial infections can destroy (necrosis) soft tissues and, if left untreated, can be life-threatening (Fournier gangrene, gas gangrene, and necrotizing fasciitis).
A review of 1,583 patient reports found that supplemental hyperbaric oxygen therapy cured severe cases of soft tissue bacterial infections and increased survival [56].
In bacterial infections, hyperbaric oxygen therapy reduced swelling, stimulated tissue growth, inhibited bacterial toxin production, enhanced antibiotic efficiency, and protected against infections [57].
Gas Gangrene
Gas gangrene is the result of an extremely dangerous, often deadly Clostridium infection in a wound. Hyperbaric oxygen therapy is used to reduce mortality and amputation rates [58].
Flesh-Eating Disease
Necrotizing fasciitis, or flesh eating disease, is a rare but potentially deadly disease caused by a bacterial infection underneath the skin, usually in someone with a compromised immune system. Hyperbaric oxygen therapy not only reduces mortality rates in people with flesh eating disease, but it reduces the amount of tissue that needs to be removed due to the infection [59].
Potential Future or Off-Label Uses
Hyperbaric oxygen therapy has been observed to be beneficial for the following conditions in clinical trials, and some doctors may recommend its use. However, it’s important to remember that HBOT is a medical procedure which should be supervised by a medical professional. Your doctor will determine whether HBOT might be appropriate in any given circumstance.
13) Vision Loss
Obstruction of eye blood vessels (central retinal artery and vein occlusion and branch retinal artery occlusion) is a common cause of blindness in elderly patients [60].
In 2 elderly patients with acute blindness, 8 to 9 sessions of hyperbaric oxygen therapy significantly improved sight [60].
In young people, certain genetic mutations (factor V Leiden mutation, methylenetetrahydrofolate reductase mutation) can also block the retinal artery and vein [61, 62].
Supplemental hyperbaric oxygen therapy for 20 days prompted visual recovery of a teenager with branch retinal artery occlusion caused by a mutation in the protein methylenetetrahydrofolate reductase (MTHFR gene) [62].
In a patient with combined central retinal artery and vein occlusions caused by factor V Leiden mutation, urgent administration of 9 sessions of hyperbaric oxygen therapy improved vision [61].
In one rare case, exposure to high altitude can block the retinal artery and cause vision loss. A patient suffering from visual loss due to high altitude exposure regained her sight after treatment with hyperbaric oxygen therapy for 11 days [63].
Along with increasing oxygen supply to the eye’s tissues, hyperbaric oxygen therapy may also reduce swelling of the retina [60, 61, 64].
14) Chronic Pain
Hyperbaric oxygen therapy in 60 patients (RCT) with a chronic pain disorder (fibromyalgia) for 8 weeks improved brain and nerve activity [65].
In a patient suffering from chronic muscle/bone disease (Complex Regional Pain Syndrome), 3 weeks of hyperbaric oxygen therapy reduced swelling, pain, and improved motion of the lower limbs [66].
As hyperbaric oxygen therapy decreases pain, it also reduces dependence on painkillers in patients with chronic pain [67].
Cellular death of bone tissue (osteonecrosis) is most commonly attributed to an interruption of blood supply. In multiple bone cell studies (osteoblasts/osteoclasts), hyperbaric oxygen therapy promoted the generation of bone mass and prevented bone loss [68, 69].
15) Brain Injuries and Trauma
In 60 patients with spinal injuries (RCT), hyperbaric oxygen therapy for 8 weeks improved nerve function and reduced depression and anxiety [70].
A meta-analysis of 8 studies of patients with traumatic brain injuries showed that hyperbaric oxygen therapy significantly improved survival rate [71].
A systematic review of 11 studies with 705 patients (RCT) determined that hyperbaric oxygen therapy decreased disability and improve brain activity [72].
In a 2-year-old girl suffering from a brain injury, 27 days of hyperbaric oxygen therapy restored the loss of brain tissue and resulted in complete recovery [73].
However, a meta-analysis of 571 patients with traumatic brain injury showed that using hyperbaric oxygen therapy in addition to standard treatments was not beneficial. Patients had improved survival outcomes initially, but long-term symptoms remained in those who were not treated immediately [74].
In multiple rat models of brain injury, hyperbaric oxygen therapy reduced inflammation, inhibited nerve injury, increased the growth of nerve cells and blood vessels, and reduced pain [75, 76, 77, 78, 79].
In rats, hyperbaric oxygen therapy protected the brain by decreasing the production of inflammatory factors and improving the antioxidant defense pathways [80, 81].
In rat models, hyperbaric oxygen therapy induced the production of heat shock proteins and cellular pathways that protect spinal neurons against oxidative injury [82, 83].
A study with immune cells from severely injured patients found that a single session of hyperbaric oxygen therapy suppressed inflammation [84].
16) Hearing Loss
The sensorineural hearing loss is a condition caused by the loss of nerves or cells within the ear. It accounts for about 90% of hearing loss and deafness [85].
A review of clinical data from 167 patients showed that adjunctive hyperbaric oxygen therapy is effective in treating patients with sensorineural hearing loss [86].
In guinea pigs, hyperbaric oxygen therapy for 4 weeks upregulated protective enzymes in the inner ear (cochlea) [87].
17) Fungal Infections
Mucormycosis, a life-threatening invasive fungal infection, affects people with a suppressed immune response [88].
A patient with a blood disorder (thalassemia) was found to be cured of fungal wound infections after 40 sessions of hyperbaric oxygen therapy [89].
Twenty sessions of hyperbaric oxygen therapy also cleared a fungal infection in an elderly patient with diabetes and liver failure [90].
Hyperbaric oxygen therapy also increases the production of free radicals, which helps to combat fungus [91].
However, long-term production of free radicals can result in oxidative stress and cell damage [92].
18) Dementia and Alzheimer’s Disease
In an analysis of 64 patients taking donepezil (RCT), a drug that treats Alzheimer’s, patients receiving additional hyperbaric oxygen therapy for 12 weeks had significantly more cognitive improvements [93].
In a patient with post-operative dementia, 40 sessions of hyperbaric oxygen therapy in addition to other therapies improved cognition and reduced confusion. It also improved memory, social interaction, sleep patterns, and physical independence [94].
In multiple rat models of Alzheimer’s disease, hyperbaric oxygen reduced inflammation, and proteins linked to Alzheimer’s [95, 96].
In a rat model of Alzheimer’s disease, hyperbaric oxygen therapy improved cognitive ability and reduced brain damage [97].
19) Frostbite
In a case study of 2 patients suffering from frostbite, 25 to 30 sessions of hyperbaric oxygen therapy preserved tissue health and promoted recovery of the dead tissue [98].
Cancer Research
Hyperbaric oxygen therapy in human cancer patients is a contentious topic of research. A few clinical trials have been performed, but these have produced conflicting results across patients with different types of cancer. As such, HBOT has not been approved as part of any cancer treatment [99].
Many cell studies have shown that hyperbaric oxygen therapy is beneficial in reducing tumor growth. Although oxygen therapy promotes blood vessel growth in normal cells, hyperbaric oxygen therapy reduces blood vessel formation around tumor cells. This decreases the supply of oxygen to the cancerous tissue, promoting death [99, 100, 101].
In mice injected with human breast cancer cells, hyperbaric oxygen therapy reduced the spread of cancerous cells and suppressed tumor growth [102].
Contraindications
Hyperbaric oxygen therapy is a potentially dangerous medical procedure that should only be performed under medical supervision.
Before using supplemental oxygen therapy, patients must be inspected for pneumothorax. Pneumothorax is caused by the buildup of air in the space between the chest wall and the lungs. If the pneumothorax is unrecognized or untreated, using oxygen therapy could result in the lungs collapsing and ultimately death [103, 2].
Oxygen constricts blood vessels, and hyperbaric oxygen therapy might increase pressure on the heart. Patients with a history of congestive heart failure are also at risk of adverse effects [103, 2].
Other risk factors include [103, 2]:
- Hyperthyroidism
- Severe claustrophobia
- Febrile illness
- Chronic obstructive pulmonary disease (COPD)
- Seizure disorder
Highly concentrated oxygen can easily catch on fire. Therefore, fires surrounding hyperbaric oxygen chambers, oxygen gas cylinders, tanks, and concentrators are a high risk of danger [103].
Despite the risks and side effects, proper use of hyperbaric oxygen therapy is generally considered a safe and low-risk intervention when performed by a medical professional [104].
Side Effects
Due to the high pressure, hyperbaric oxygen therapy has more risks than normobaric therapy. These include [103, 105, 106, 2, 107]:
- Retinopathy in premature babies: When the blood vessels connecting to the eyes do not develop (retinal vessels)
- Bronchopulmonary dysplasia in premature babies: Results in lung dysfunction (respiratory distress syndrome). Oxygen therapy is therefore not recommended for infants and children.
- Inflammation of the lining of undeveloped lungs
- Injured airways
- Production of breathing difficulties and lung dysfunction
- Can result in asthma-like symptoms and exercise intolerance
- Production of oxidative stress that could potentially result in seizures
- Barotrauma to the ears and sinuses (mild)
- Short-term short-sightedness (myopia)
- Accelerated cataract growth in eyes
Hyperbaric oxygen therapy can also cause distress in patients suffering from claustrophobia, high blood pressure, and low blood glucose, and can cause heart failure [103].
