Several therapeutic principles are made use of in HBOT:
The United States, the Undersea and Hyperbaric Medical Society, known as UHMS, approved for reimbursement diagnoses for application of HBOT in hospitals. The following approved indications are approved uses of hyperbaric oxygen therapy as defined by the UHMS Hyperbaric Oxygen Therapy Committee. The Committee Report can be purchased directly through the UHMS
In the United States, HBOT is recognized by Medicare as a reimbursable treatment for 14 UHMS "approved" conditions. An HBOT session costs anywhere from $100 to $200 in private clinics, to over $1,000 in hospitals. More U.S. physicians are lawfully prescribing HBOT for "off label" conditions such as Lyme Disease, stroke, migraines and also in Autism and related disorders like ADHD. Such patients are treated in outpatient clinics, however it is unlikely that their medical insurance will pay for off label treatments. In the United Kingdom most chambers are financed by the National Health Service, although some, such as those run by Multiple Sclerosis Therapy Centres, are non-profit.
HBOT is controversial and health policy regarding its uses is politically charged. Both sides of the controversy on the effectiveness of HBOT is available in the form of PubMed and the Cochrane reviews and a discussion of "Medical Polemics, a discussion of Multiple Sclerosis in particular.
The traditional type of hyperbaric chamber used for HBOT is a hard shelled pressure vessel. Such chambers can be run at absolute pressures up to 600 kilopascals or 85 PSI (lbf/in²), nearly six atmospheres.
Navies, diving organizations and hospitals typically operate these. They range in size from those which are portable and capable of treating just one patient to those which are fixed, very heavy and capable of treating eight or more patients.
The chamber may consist of:
In today's larger "multiplace" chambers, both patients and medical staff inside the chamber breathe from "oxygen helmets", flexible, transparent soft plastic helmets with a seal around the neck similar to a space suit helmet, or tightly fitting aviators oxygen masks, which supply pure oxygen and remove the exhaled gas from the chamber. During treatment patients breathe 100% oxygen most of the time but have periodic air breaks 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 provoke a fire. Medical staff may also breathe oxygen to reduce the risk of decompression sickness. Administration of 100% breathing oxygen maximizes the patients treatment. The pressure inside the chamber is increased by opening valves allowing high-pressure air to enter from storage cylinders, similar to diving cylinders. A gas compressor is used to fill these cylinders. Smaller "monoplace" chambers can only accommodate the patient. No medical staff can enter. The chamber is flooded with pure oxygen or compressed air. The cost of using pure oxygen in a monoplace chamber is much higher than using compressed air. If pure oxygen is used no oxygen breathing mask or helmet is needed. If compressed air is used then an oxygen mask or helmet is needed as in a multiplace chamber. In monoplace chambers that are compressed with pure oxygen a mask is available to provide the patient with "air breaks," periods of breathing normal air, in order to reduce the risk of hyperoxic seizures.
To reduce the pressure, a valve is opened to allow gas 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.
There are portable HBOT chambers, which are used for home treatment. These are usually referred to as "mild chambers", which is a reference to the lower pressure of soft-sided chambers. Those commercially available in the USA go up to 4 PSI (1.27 ATA 8.92 FSW). International portable chambers can go to 7.35 psi (1.5 ATA 16.38 FSW) or higher. These chambers are operated with oxygen concentrators (typically 95% oxygen) or with 100% oxygen as the breathing gas.
The soft chambers are FDA approved only for the treatment of Altitude Sickness but are commonly used off label primarily for the treatment of autism and other neural conditions. The FDA has a specific warning that supplemental oxygen is not to be used. Terrell Owens of the Dallas Cowboys has one in his house to aid his recovery from injuries as well as teammate Kevin Burnett. Similarly, Jimmy Rollins of the Philadelphia Phillies reported he has one he is using to speed recovery from a sprained ankle. J.D. Drew of the Boston Red Sox has one as does Zach Thomas of the Dallas Cowboys and Darren Sharper of the Minnesota Vikings.
The slang term 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.
Emergency HBOT for diving disorders typically follows one of two forms. For most cases, a shallow "dive" to a pressure the equivalent of 18 meters / 60 feet of water for 3 to 4.5 hours with the casualty breathing pure oxygen with air breaks every 20 minutes to reduce oxygen toxicity. For extremely serious cases, a deeper "dive" to a pressure the equivalent of 37 meters / 122 feet of water for 4.5 hours with the casualty breathing air.
In Canada and the United States, the U.S. Navy Dive Charts are used 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 which compiles the latest research findings and contains information regarding the recommended duration and pressure of the longer-term conditions.
There 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 for long periods can cause oxygen toxicity. Temporarily blurred vision can be caused by swelling of the 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).
Also, patients should not undergo HBO therapy if they are taking or have recently taken the following drugs:
The following are relative contraindications:
The Collet (Quebec) trial that was published in the Lancet in 2001 was the largest randomized trial of Hyperbaric Oxygen Therapy (HBOT) for children with cerebral palsy (CP); it followed the McGill pilot study on the same subject.
The evidence showed both groups of children treated with two very different hyperbaric treatment dosages improved significantly. The motor improvements that were seen and measured with the gross motor function measure were greater, more generalized, and were obtained in a shorter period of time than most of the changes found in any other studies of recognized conventional therapies in the treatment of children with cerebral palsy. The children in both groups improved an average of ten times more during the two months of HBOT (whilst all other therapies and medication were stopped) than during the three months follow-up (when medication and all the ancillary treatments were restarted). This impressive change in the rate of improvements clearly indicates the probable effectiveness of hyperbaric treatment. Both the Lancet commentary and the tech report by the Agency for Healthcare Research and Quality (AHRQ) concluded that the hypothesis of both treatments being equally effective should be retained.
Since the Quebec study of HBOT for children with CP, many reports have been made on the possible efficacy of a low pressure hyperbaric treatment and all the trials conducted with HBOT in CP have demonstrated positive results.
An editorial on CP published by the Undersea and Hyperbaric Medical Society in 2007 called for further research that will include "basic science research to determine a reasonable mechanism of action" for hyperbaric oxygenation as well as "clinical studies of the highest possible methodological rigor".
Middle ear barotrauma (MEBT) is always a consideration in treating both children and adults in a hyperbaric environment, but most children currently being treated with HBOT are being pressurized to 1.3 ATA which greatly reduces the risks of potential side effects of any kind.
Some medical practitioners recommend the use of HBOT for the treatment of acute tinnitus but this treatment has not been verified by independent evidence and the treatment was withdrawn from support by the German health insurance. There is evidence that the therapeutic effects could be greatly due to psychological mechanisms triggered by the patients attitude towards therapy prior to the treatment.
It has been postulated that HBOT might relieve some of the core symptoms of autism..
Fischer et al. in New York University performed the first randomized, placebo-controlled, double-blind trial on MS patients treated with HBOT. Improvements in balance and bladder function were found in 12 of 17 patients (p<0.0001). Those patients with a less severe form of the disease had a more favorable and long lasting response. After a year with no further treatment, the treated group showed a positive change (p<0.0008). Barnes et al. found overall benefit in their treated group (p<0.03) and a year later there was less deterioration in cerebellar function (p<0.03). Two other controlled studies have reported sustained benefit with follow-up.
In the 2004 Cochrane review, Bennett and Heard "found no consistent evidence to confirm a beneficial effect of hyperbaric oxygen therapy for the treatment of multiple sclerosis and do not believe routine use is justified".