Therapeutic principlesSeveral therapeutic principles are made use of in HBOT:*
IndicationsIn the United States the Undersea and Hyperbaric Medical Society, known as UHMS, lists approvals for reimbursement for certain diagnoses in hospitals and clinics. The following Indication (medicine)|indications are approved (for reimbursement) uses of hyperbaric oxygen therapy as defined by the UHMS Hyperbaric Oxygen Therapy Committee:* However, these are reimbursement decisions based on cost of medical treatments vs HBOT at the average U.S. hospital charge of $1,800.00 per 90 minute HBOT treatment. China and Russia treat more than 80 maladies, conditions and trauma with HBOT, since costs are insignificant in those countries.*
Other reported applications include:
ContraindicationsThe only absolute contraindication to hyperbaric oxygen therapy is untreated tension pneumothorax.* The reason is concern that it can progress to tension pneumothorax, especially during the decompression phase of therapy. The COPD patient with a large bleb represents a relative contraindication for similar reasons.* Also, the treatment may raise the issue of Occupational health and safety (OHS), which has been encountered by the therapist.*
Patients should not undergo HBO therapy if they are taking or have recently taken the following drugs:
The following are relative contraindications -- meaning that special consideration must be made by specialist physicians before HBO treatments begin:
Pregnancy is not a relative contraindication to hyperbaric oxygen treatments,* although it may be for SCUBA diving. In cases where a pregnant woman has carbon monoxide poisoning there is evidence that lower pressure (2.0 ATA) HBOT treatments are not harmful to the fetus, and that the risk involved is outweighed by the greater risk of the untreated effects of CO on the fetus (neurologic abnormalities or death.)* In pregnant patients, HBO therapy has been shown to be safe for the fetus when given at appropriate levels and “doses” (durations). In fact, pregnancy lowers the threshold for HBO treatment of carbon monoxide-exposed pregnant patients. This is due to the high affinity of fetal hemoglobin for CO.*
ConstructionThe traditional type of hyperbaric chamber used for HBOT is a hard shelled pressure vessel. Such chambers can be run at absolute pressures as much as , . Navies, diving organizations, hospitals, and dedicated recompression facilities typically operate these. They range in size from semi-portable, one-patient units to room-sized units that can treat eight or more patients. Recent advances in materials technology have resulted in the manufacture of portable, "soft" chambers that can operate at between above atmospheric pressure.* Hard chambers and soft chambers should not be considered equivalent in regards to efficacy and safety as they are different in many aspects.
A hard chamber may consist of
A soft chamber may consist of
Oxygen supplyIn today's larger multiplace chambers, both patients and medical staff inside the chamber breathe from either "oxygen hoods" – flexible, transparent soft plastic hoods with a seal around the neck similar to a space suit helmet – or tightly fitting oxygen masks, which supply pure oxygen and may be designed to directly exhaust the exhaled gas from the chamber. During treatment patients breathe 100% oxygen most of the time to maximise the effectiveness of their treatment, but have periodic "air breaks" during which they breathe room air (21% oxygen) to minimize the risk of oxygen toxicity. The exhaled gas must be removed from the chamber to prevent the build up of oxygen, which could present a fire risk. Attendants may also breathe oxygen to reduce their risk of decompression sickness. The pressure inside a hard chamber is increased by opening valves allowing high-pressure air to enter from Gas cylinder|storage cylinders, which are filled by an air compressor. A soft chamber may be pressurised directly from a compressor.
Smaller "monoplace" chambers can only accommodate the patient, and no medical staff can enter. The chamber may be pressurised with pure oxygen or compressed air. If pure oxygen is used, no oxygen breathing mask or helmet is needed, but the cost of using pure oxygen is much higher than that of using compressed air. If compressed air is used, then an oxygen mask or hood is needed as in a multiplace hard chamber. In monoplace chambers that are compressed with pure oxygen, a mask is needed to provide the patient with "air breaks", or periods of breathing normal air (21% oxygen). This is in order to reduce the risk of hyperoxic seizures. In soft chambers, using compressed air and a mask supplying 96% oxygen, no air breaks are necessary, because the risk of oxygen toxicity is negligible because of the lower oxygen partial pressures used (usually 1.3 ATA), and short durations of treatment.
TreatmentsInitially, HBOT was developed as a treatment for Diving hazards and precautions|diving disorders involving bubbles of gas in the tissues, such as decompression sickness and gas embolism. The chamber cures decompression sickness and gas embolism by increasing pressure, reducing the size of the gas bubbles and improving the transport of blood to downstream tissues. The high concentrations of oxygen in the tissues are beneficial in keeping oxygen-starved tissues alive, and have the effect of removing the nitrogen from the bubble, making it smaller until it consists only of oxygen, which is re-absorbed into the body. After elimination of bubbles, the pressure is gradually reduced back to atmospheric levels. Hyperbaric Chambers are also used for animals, especially race horses where a recovery is worth a great deal to their owners. It isalso used to treat dogs and cats in pre and post surgery treatment to strengthen their systems prior to surgery and then accelerate healing post surgery.
ProtocolThe slang term, at some facilities, for a cycle of pressurization inside the HBOT chamber is "a dive". An HBOT treatment for longer-term conditions is often a series of 20 to 40 dives, or compressions. Again, these dives last for about an hour and can be administered via a hard, high-pressure chamber or a soft, low-pressure chamber - the major difference being per-dive "dose" of oxygen. Many conditions do quite well with the lower dose, lower cost-per-hour, soft chambers.
Emergency HBOT for decompression illness follows treatment schedules laid out in treatment tables. Most cases employ a recompression to absolute, the equivalent of of water, for 4.5 to 5.5 hours with the casualty breathing pure oxygen, but taking air breaks every 20 minutes to reduce oxygen toxicity. For extremely serious cases resulting from very deep dives, the treatment may require a chamber capable of a maximum pressure of , the equivalent of of water, and the ability to supply heliox as a breathing gas.*United States Navy|U.S. Navy treatment charts are used in Canada and the United States to determine the duration, pressure, and breathing gas of the therapy. The most frequently used tables are Table 5 and Table 6. In the UK the Royal Navy 62 and 67 tables are used.
The Undersea and Hyperbaric Medical Society (UHMS) publishes a report that compiles the latest research findings and contains information regarding the recommended duration and pressure of the longer-term conditions.*
Home and out-patient clinic treatmentThere are several sizes of portable chambers, which are used for home treatment. These are usually referred to as "mild personal hyperbaric chambers," which is a reference to the lower pressure (compared to hard chambers) of soft-sided chambers. Food and Drug Administration (FDA) approved chambers for use with room air are available in the USA and may go up to 4.4 pounds per square inch (psi) above atmospheric pressure, which equals 1.3 atmospheres absolute (ATA), equivalent to a depth of 10 feet of sea water. In the US, these "mild personal hyperbaric chambers" are categorized by the FDA as CLASS II medical devices and requires a prescription in order to purchase one or take treatments.* Personal hyperbaric chambers are only FDA approved to reach 1.3 ATA. While hyperbaric chamber distributors and manufacturers cannot supply a chamber in the US with any form of elevated oxygen delivery system, a physician can write a prescription to combine the two modalities, as long as there is a prescription for both hyperbarics and oxygen. The most common option (but not approved by FDA) some patients choose is to acquire an oxygen concentrator which typically delivers 85–96% oxygen as the breathing gas. Because of the high circulation of air through the chamber, the total concentration of oxygen in the chamber never exceeds 25% as this can increase the risk of fire. Oxygen is never fed directly into soft chambers but is rather introduced via a line and mask directly to the patient. FDA approved oxygen concentrators for human consumption in confined areas used for HBOT are regularly monitored for purity (+/- 1%) and flow (10 to 15 liters per minute outflow pressure). An audible alarm will sound if the purity ever drops below 80%. Personal hyperbaric chambers use 120 volt or 220 volt outlets. Ranging in size from 21 inches up to 40 inches in diameter these chambers measure between 84 in (7 ft) to 120 in (10 ft) in length. The soft chambers are approved by the FDA for the treatment of altitude sickness, but are commonly used for other "off-label" purposes.
Possible complications and concernsThere are risks associated with HBOT, similar to some diving disorders. Pressure changes can cause a "squeeze" or barotrauma in the tissues surrounding trapped air inside the body, such as the lungs,* behind the eardrum,* inside paranasal sinuses,* or trapped underneath dental fillings.* Breathing high-pressure oxygen may cause oxygen toxicity.* Temporarily blurred vision can be caused by swelling of the lens (vision)|lens, which usually resolves in two to four weeks.*There are reports that cataract may progress following HBOT.* Also a rare side effect has been blindness secondary to optic neuritis (inflammation of the optic nerve).
Effects of PressurePatients inside the chamber may notice discomfort inside their ears as a pressure difference develops between their middle ear and the chamber atmosphere.* This can be relieved by the Valsalva maneuver or by "jaw wiggling". As the pressure increases further, mist may form in the air inside the chamber and the air may become warm. Increased pressure may also cause ear drums to rupture, resulting in severe pain.
To reduce the pressure, a valve is opened to allow air out of the chamber. As the pressure falls, the patient's ears may "squeak" as the pressure inside the ear equalizes with the chamber. The temperature in the chamber will fall. The speed of pressurization and de-pressurization can be adjusted to each patient's needs.
NeurologicalCerebrovascular diseases occur due to insufficient oxygen supply to central neural tissue. When that happens, the primary damage of brain tissue cannot recover and it is a leading cause of death. Adequate therapy with oxygen supply can minimize secondary tissue impairment and can restore the neuronal function. Therapy with HBO reopens occluding vessels and is essential for the survival of neural tissue.* In addition, HBOT regenerates axons to reinstate the functioning of nerves.* The clinical experience and results so far published has promoted the use of HBO therapy in patients suffering from cerebrovascular injury and focal cerebrovascular injuries.* However, the power of clinical research is limited because of the shortage of randomized controlled trials.
DiabetesWhen suffering from Type 1 Diabetes, HBOT might be a useful therapy. The health of diabetic rats improved drastically after hyperbaric oxygen therapy because of the higher blood glucose levels and increased muscle oxygenation in the region of the feet. These effects potentially have a beneficial influence on future presentation of a diabetic ulcer.* In addition, there also are signs that HBOT may have an immunologic benefit in Type 1 Diabetes. The destructive effect of diabetes on pancreatic beta cells can be inhibited by increasing activity of resting T-cells and diminishing activity of dendritic cells, both of which may be affected by HBOT.* However, this therapy might only be helpful in a pre-emptive timeframe. No evidence has been found on beneficial oxygen therapy response, when already in a prediabetic stage. Therefore, HBOT can induce both positive and negative effects, depending on the phase of the disease.*
Radiation woundsThere has been positive results for neoadjuvant HBOT in combination with radiotherapy. After this therapy, tumors showed an apparent growth delay.* On the other hand, HBOT inhibits both the growth and differentiation of osteoblasts These effects could have a negative effect on necrotic tissue proliferation and bone generation, which would not help in therapy of radiation wounds.* Many studies indicate a positive share of HBOT after radiation injury, and HBOT is prescribed for treating chronic wounds associated with radiation exposure. However, no significant evidence was found on HBOT having either a positive or negative effect on radiation wounds. This might be explained due to the lack of experimental and clinical studies.*
Chronic UlcersA review in 2012, focusing on diabetic foot ulcers, concluded that HBOT, while increasing the rate of early ulcer healing, did not provide any benefit in wound healing at long term follow up. In particular, there was no difference in major amputation rate. For venous, arterial and pressure ulcers, no evidence was apparent that HBOT provides an improvement on standard treatment.*
Neurological and RadiationThere are signs that HBOT might improve outcome in late radiaton tissue injury affecting bone and soft tissues of the head and neck. In general patients with radiation injuries in the head, neck or bowel showed an improvement in quality of life after HBO therapy. On the other hand, no such effect was found in neurological tissues. The use of HBOT may be justified to selected patients and tissues, but further research is required to establish the best patient selection and timing of any HBO therapy.*
Neuro-rehabilitationA 2004 systematic review of HBOT in traumatic brain injury identified 2 randomized controlled trials and 5 observational studies that met evaluated functional health outcomes. The studies ranged from fair to poor in quality. None adequately reported adverse events, the most serious reported being seizures, pulmonary symptoms, and neurologic deterioration. The review concluded there was insufficient evidence to prove the effectiveness or ineffectiveness, including risks and benefits of HBOT for TBI. In one RCT, the HBOT group had reduced mortality compared to the control group but much higher levels of disability. Another, smaller, study found no difference in mortality. The observational studies were weak in quality and did not provide enough evidence of clinical improvement following HBOT treatment.*Evidence in a 2005 systematic review of the evidence for HBOT in the treatment of stroke showed no benefit to the treatment, though the generalizability of the finding was limited due to the wide variety in stage and type of stroke, and the treatment given. Good quality studies were recommended to determine if HBOT provides any benefit in stroke.* Another review that examined the effectiveness of HBOT in acute stroke. It found no evidence that HBOT improved clinical outcomes at 6 months, but further study was recommended.*
A systematic review of HBOT for cerebral palsy was published in 2007. Two randomized controlled trials and four observational studies were identified.* The best evidence from a randomized controlled trial (the Collet study) found that HBOT and slightly pressurized room air resulted in similar improvements in motor function of about 5–6% compared to baseline.* Neuropsychological tests also showed no difference between HBOT and room air. Based on caregiver report, those who received room air had significantly better mobility and social functioning.* Several methodological concerns about the study were raised. Another trial found no difference between a HBOT and a no treatment group.* Some low quality observational studies of HBOT reported similar improvements in motor function. Children receiving HBOT were reported to experience seizures and the need for tympanostomy tubes to equalize ear pressure, though the incidence was not clear. Future research was recommended to determine the efficacy of pressurized room air and non-pressurized oxygen compared with standard treatments.*A 2010 review of 12 randomized studies using HBOT with multiple sclerosis suggested that there is no clinically significant benefit from the administration of HBOT. The review proposed that more trials for selected subgroups of MS and for prolonged treatments may be worthwhile, but routine use of HBOT in the treatment of MS was not recommended.* A 2004 Cochrane review, however, concluded that further "trials are not, in our view, justified."*