“These findings confirm what we are seeing in clinical practice — that many children with autism may benefit with the use of this treatment,” Rossignol said.

Hyperbaric oxygen therapy involves having a patient inhale oxygen pressurized to a level greater than atmospheric pressure. While anecdotal evidence has already led many physicians to begin experimenting with the therapy as a treatment for autism, the current study is the first large scale, double-blind controlled clinical trial into its effectiveness.

Rossignol randomly assigned 62 autistic children between the ages of two and seven to inhale either air that consisted of 24 percent oxygen at 1.3 atm or only slightly pressurized air (1.03 atm) consisting of 21 percent oxygen for 40 sessions of one hour each. The treatment took place at six different centers across the United States.

After 40 hours of treatment, children in the hyperbaric (1.3 atm) treatment group showed significantly improvement in measures of eye contact, sensory and cognitive awareness, social interaction, receptive language and overall functioning, compared to children in the control (1.03 atm) group.

“We’re not saying it’s a cure,” Rossignol said, “but … if you can improve understanding so a kid doesn’t run in front of a car, or improve sleep, that would be a benefit.”

Researchers do not know what mechanisms hyperbaric therapy might act through to improve the symptoms of autism, but Rossignol hypothesized that it might help reduce the inflammation that constricts blood flow to the speech centers of autistic children’s brains. It might also improve the brain’s overall ability to absorb oxygen, with similar effects.

“With autism on the rise, it is promising to see a study that has been conducted with the high standards endorsed by the medical community,” said Shannon Kenitz of the International Hyperbarics Association. “Having this scientifically controlled and analyzed study that shows the positive effects of hyperbarics is truly what this community has needed.”

While increasing tissue-oxygen levels is a primary therapeutic effect of HBOT, other benefits include reducing edema, modifying growth factors and cytokine effects, stimulating more rapid development of capillary budding and granulation tissue formation within the wound bed, promoting cellular proliferation, accelerating collagen deposition, and increasing microbial oxidative killing.

Damaged tissue can have decreased oxygen levels that reduce the activity of several antibiotics, including aminoglycosides, sulfonamides, and fluoroquinolones. By raising the oxygen in ischemic tissue to normal levels, HBOT may normalize the activity of these antimicrobials. Additionally, HBOT may potentiate the activity of certain antimicrobials by inhibiting biosynthetic reactions in bacteria. HBOT can modulate the immune system response and also enhance oxygen-radical scavengers, thereby decreasing ischemia-reperfusion injury.

Although any therapeutic application of hyperbaric oxygenation is intrinsically associated with the potential for producing mild-to-severe side effects, the appropriate use of hyperoxia is one of the safest therapeutics available to the practitioner.

It is unknown if hyperbaric oxygen therapy will cause congenital defects in horses. In human studies it has not been shown to have adverse effects. In our hyperbaric center, we do not hesitate to treat a mare with HBOT, especially when the benefits outweigh the risks. It is not unusual in our clinic, if treating a foal, to allow the mare in the chamber during treatments to aid in the relaxation of the foal.

In the 17th century bridge construction demanded workers dive to great underwater depths with the introduction of caissons (a chamber, usually of steel but sometimes of wood or reinforced concrete, used in the construction of foundations or piers in or near a body of water). The air in the chamber is kept under pressure great enough to prevent the entrance of water, while shafts through the bulkhead permit the passage of workers, equipment, and excavated material between the bottom and the surface. Workers frequently suffered from caisson’s disease (the “bends”) and were treated in metallic vessels large enough to hold people and strong enough to hold air under pressure. These vessels, combined with newly-developed air compressors, resulted in the enabled treatment of patients with hyperbaric air decompression. This represented the first reports of decompression sickness; the caisson workers assumed a bent posture (the “bends”) to help relieve the pain caused by nucleation of accrued nitrogen in their joints as they emerged from depths of up to 70 feet.

Conventional western medicine uses HBOT to treat the following:

Uncontrolled Decompression during Diving: results in one of two types of decompression sickness (DCS).

*DCS I involves only the extremities (arms/legs) and the joints
*DCS II involves the central nervous system (brain/spinal cord)

Treatment involves recompressing the patient in 100% oxygen, followed by controlled decompression using data developed by the U.S. Navy.

Carbon Monoxide Poisoning: This colorless, odorless gas passes readily through alveoli (lung tissue air sacs) into the blood where it binds tightly to oxygen-carrying proteins in the blood (hemoglobin). Carbon monoxide also locks up the energy factory machinery (cytochrome system) inside each cell’s mitochondria. This prevents our bodies from being able to use oxygen. The use of HBOT to treat carbon monoxide poisoning is controversial. It is used to prevent/treat the development of neurologic injury in patients with severe exposure to this deadly gas. Usually, patients undergo one or two 90-minute treatments at 2-3 atmospheres (2-3 times the atmospheric pressure at sea level).

Difficult Wounds: Chronic, non-healing wounds are found in a variety of clinical patients. Recent data has supported the use of HBOT in the treatment of non-healing wounds caused by irradiation. There is less data to support the use of HBOT in other clinical settings. However, HBOT is often recommended in patients with difficult clinical problems. For example, diabetes mellitus and vascular disease are notorious for late complications of non-healing wounds. Amputation of an infected lower leg is the end result in many unfortunate cases. These patients have been shown, recently, to benefit from HBOT. One study showed decreased major amputation rate in diabetic patients who underwent HBOT (30 daily 90-minute treatments at 2-3 atmospheres).

Soft Tissue Infections: with anaerobic bacteria had a lower mortality rate in patients who underwent hyperbaric oxygen therapy, according to one study. Another study showed HBOT to have no benefit in these infections. According to one author (Sheridan), HBOT seems a reasonable adjunct to surgery, if it can be safely administered without delaying standard treatment (surgery and antibiotics). Treatment would consist of 90-minute treatments at 2-3 atmospheres once or twice daily.

Alternative Medicine

Stroke: Although HBOT is used conventionally in the United States, its use is reportedly higher in other countries. Stroke patients in Germany may undergo this form of treatment according to David Hughes, D.Sc. of the Hyperbaric Oxygen Institute. Hughes states that HBOT has decreased the aftercare costs for stroke patients in Germany by as much as 71%. As recent as 1995, one French study (Nighoghossian) showed that HBOT may be helpful in the treatment of ischemic stroke. But more recent investigations (Rusyniak et al) have shown that HBOT “does not appear to be beneficial and may be harmful in patients with acute ischemic stroke”.

Peripheral Vascular Disease and Chronic Wounds: Hughes also claims that HBOT is used in France for peripheral vascular disease (PVD); which can be caused by atherosclerosis, arteriosclerosis, and diabetes, and others. PVD oftentimes results in poor wound-healing and chronic ulcers (most often on/around the foot and ankle). HBOT is not part of routine, conventional wound care for diabetic foot ulcers. It may, however, be considered for some patients. The American Diabetes Association recognizes HBOT as a potential adjunctive therapy for complex limb-threatening diabetic foot wounds unsuitable for revascularization procedures.

Multiple Sclerosis: Dr. Hughes also states that HBOT is used in Great Britain to treat Multiple Sclerosis (MS). Based on an unpublished article from 1993 by D. Perrin, Hughes cites that more than 25,000 MS patients have benefited from HBOT. But, according to Kleijnen, patients who have chronic progressive or chronic stable multiple sclerosis showed no consistent positive effects to HBOT (results based on Expanded Disability Status Score [EDSS] and the Functional Status Score). An earlier study by Kindwall (1991) treated patients in accordance with protocols that reported to produce a benefit in multiple sclerosis. Investigators were unable to substantiate any useful long-term effect of hyperbaric oxygen therapy.

The French surgeon Fontaine built a mobile compressorized operating suite in 1879. Patients reportedly had better outcomes because of improved oxygenation and decreased postoperative vomiting and cyanosis. Easier reduction of hernias was noted. Corning introduced the therapeutic compression chamber to the US in 1891 to treat nervous and mental afflictions. This chamber was the first operated by electric power.

Orville Cunningham noted 25 years later that patients with certain cardiovascular disorders improved when moved from high altitudes to sea-level altitudes. He discovered this during the Spanish flu epidemic in 1918, which resulted in more than 500,000 deaths. Many of these victims died in a cyanotic state. Under the care of Dr Cunningham, a rather sick resident physician was treated in the compression chamber and recovered completely. Cunningham subsequently built an 88-ft long and 10-ft wide chamber to treat numerous patients, with remarkable success. The credibility of the compression chamber was reinforced during treatment of flu patients. One night when the chamber’s power accidentally was shut off, all patients died. At the time, the interpretation credited hyperbaric therapy with keeping the patients alive. When the compression stopped, these patients died. However, the deaths were likely the result of rapid ascent from the compression rather than the secondary effects of the Spanish flu.

In 1928, Mr Timkin, an appreciative patient whose uremic state was resolved after receiving hyperbaric therapies, constructed for Cunningham an enormous 60-ft tall, 6-story hyperbaric hospital that looked like a steel sphere. Conditions such as hypertension, diabetes, syphilis, and cancer were treated here until 1930, when the local medical society closed the hyperbaric hospital for lack of scientific evidence or merit. After 1930, much of the medical or scientific community did not look favorably upon the use of hyperbaric medicine.

Supplemental use of oxygen increased with availability after this time. The military soon had an increased interest in underwater activities, and this promoted the use of oxygen and hyperbaric medicine for diving and decompression sickness. Hyperbaric medicine treatments had sound physiologic principles based on known physics of mixed gas when treating decompression sickness.

A flurry of interest in therapeutic hyperbaric medicine was fostered by Dr I. Boerema, who, while in Amsterdam in 1956, reported hyperbaric oxygen (HBO) as an aid in cardiopulmonary surgery, particularly for congenital conditions such as tetralogy of Fallot, transposition of great vessels, and pulmonic stenosis. A colleague of Boerema’s, W. H. Brummelkamp, also interested in hyperbaric medicine, discovered in 1959 (and subsequently published in 1961) that anaerobic infections were inhibited by hyperbaric therapy. Meanwhile, Boerema had published an article, “Life without blood,” a report of fatally anemic pigs treated successfully with volume expansion and pressurized hyperoxygenation. Boerema often is credited as the father of modern-day hyperbaric medicine.

In 1962, Smith and Sharp reported the enormous benefits of HBO in carbon monoxide poisoning. International interest thus was rekindled, and HBO therapy was thrust into the modern era. Hyperbaric units subsequently were built at Duke University, New York Mount Sinai Hospital, Presbyterian Hospital and Edgeworth Hospital in Chicago, Good Samaritan in Los Angeles, St. Barnaby Hospital in New Jersey, Harvard Children’s Hospital, and St. Luke’s Hospital in Milwaukee. Further chambers were installed in numerous international sites.

The benefits of hyperbaric medicine subsequently were observed for split-thickness skin graft acceptance, flap survival and salvage, wound re-epithelization, and acute thermal burns. These studies lent credibility to the therapeutic employment of HBO therapy. This fostered the establishment of organized scientific congresses and societies such as the International Congress on Hyperbaric Oxygen and the Undersea Medical Society. Unfortunately, as the availability of hyperbaric medicine chambers increased, the indiscriminate and inappropriate use of the chamber for a variety of medical conditions by practitioners searching for a “cure-all” therapy resulted in a backlash from the scientific society, once again tarnishing the credibility of hyperbaric medicine. As a result, by the late 1970s, the Undersea Medical Society had formulated guidelines for the use of hyperbaric therapy.

Researchers conducting wound-healing studies continued to try to take advantage of the angiogenic properties of increasing oxygen gradients resulting from hyperbaric therapy. Foot wounds from diabetes, radiation ulcers, and other ischemic wounds have been manipulated and successfully treated with HBO. Prospective blinded randomized trials and well-executed laboratory studies continue to further define the role of hyperbaric therapy in medical therapeutics.

Hyper” means increased and “baric” relates to pressure. Hyperbaric oxygen therapy (HBOT) thus refers to intermittent treatment of the entire body with 100-percent oxygen at greater than normal atmospheric pressures. The earth’s atmosphere normally exerts approximately 15 pounds per square inch of pressure at sea level. That pressure is defined as one atmosphere absolute (abbreviated as 1 ATA). In the ambient atmosphere we normally breathe approximately 20 percent oxygen and 80 percent nitrogen. While undergoing HBOT, pressure is increased up to two times (2 ATA) in 100% oxygen. In the Sechrist monoplace chambers utilized at our facilities, the entire body is totally immersed in 100-percent oxygen. There is no need to wear a mask or hood. This increased pressure, combined with an increase in oxygen to 100 percent, dissolves oxygen in the blood plasma and in all body cells, tissues and fluids at up to 10 times normal concentration—high enough to sustain life with no blood at all (from 20% to 100% oxygen is a 5-fold increase, from 1 ATA to 2 ATA can double this again to a 10-fold or 1,000% increase).

While some of the mechanisms of action of HBOT, as they apply to healing and reversal of symptoms, are yet to be discovered, it is known that HBOT:

1) greatly increases oxygen concentration in all body tissues, even with reduced or blocked blood flow;

2) stimulates the growth of new blood vessels to locations with reduced circulation, improving blood flow to areas with arterial blockage;

3) causes a rebound arterial dilation after HBOT, resulting in an increased blood vessel diameter greater than when therapy began, improving blood flow to compromised organs;

4) stimulates an adaptive increase in superoxide dismutase (SOD), one of the body’s principal, internally produced antioxidants and free radical scavengers; and,

5) aids the treatment of infection by enhancing white blood cell action and potentiating germ-killing antibiotics.

While not new, HBOT has only lately begun to gain recognition for treatment of chronic degenerative health problems related to atherosclerosis, stroke, peripheral vascular disease, diabetic ulcers, wound healing, cerebral palsy, brain injury, multiple sclerosis, macular degeneration, and many other disorders (conditions treated). Wherever blood flow and oxygen delivery to vital organs is reduced, function and healing can potentially be aided with HBOT. When the brain is injured by stroke, CP, or trauma, HBO may wake up stunned parts of the brain to restore function.

Many conditions are being treated with HBO worldwide.

For help finding a Hyperbaric Oxygen Therapy Provider near you.

One of the world’s most experienced authorities on hyperbaric medicine was Dr. Edgar End, clinical professor of environmental medicine at the Medical College of Wisconsin, who voiced his opinion on HBOT’s value for the treatment of stroke in this way: “I’ve seen partially paralyzed people half carried into the (HBOT) chamber, and they walk out after the first treatment. If we got to these people quickly, we could prevent a great deal of damage.”

Using the Sechrist monoplace chamber, HBOT is administered in a transparent, cylindrical chamber, approximately 8 feet long and 3 feet in diameter. The patient is made comfortable on a cot-like stretcher and rolled into the chamber. While in the chamber, the patient has full 360-degree vision through the transparent enclosure. The chamber is equipped with two-way microphones and speakers. The patient can watch TV, listen to music, read, nap, or talk with the chamber operator, family, or whoever is outside. During treatment, usually lasting an hour, the patient is surrounded by and inhales pure oxygen while pressure within the chamber is increased from 1-1/2 to 2 times the outside pressure. At the end of treatment, the patient is gradually decompressed to normal pressure and leaves the chamber.

Several therapeutic principles are made use of in HBOT:

* The increased overall pressure is of therapeutic value when HBOT is used in the treatment of decompression sickness and air embolism.
* For many other conditions, the therapeutic principle of HBOT lies in a drastically increased partial pressure of oxygen in the tissues of the body. The oxygen partial pressures achievable under HBOT are much higher than those under breathing pure oxygen at normobaric conditions (i.e. at normal atmospheric pressure).
* A related effect is the increased oxygen transport capacity of the blood. Under atmospheric pressure, oxygen transport is limited by the oxygen binding capacity of hemoglobin in red blood cells and very little oxygen is transported by blood plasma. Because the hemoglobin of the red blood cells is almost saturated with oxygen under atmospheric pressure, this route of transport cannot be exploited any further. Oxygen transport by plasma, however is significantly increased under HBOT.

Uses

The United States, the Undersea and Hyperbaric Medical Society, known as UHMS, approved for reimbursement diagnoses for application of HBOT in hospitals. The following indications are approved uses of hyperbaric oxygen therapy as defined by the UHMS Hyperbaric Oxygen Therapy Committee.

* Air or gas embolism
* Carbon monoxide poisoning
o Carbon Monoxide Poisoning Complicated by Cyanide Poisoning
* Clostridal Myositis and Myonecrosis (Gas gangrene)
* Crush Injury, Compartment syndrome, and other Acute Traumatic Ischemias
* Decompression sickness
* Enhancement of Healing in Selected Problem Wounds
* Exceptional Blood Loss (Anemia)
* Intracranial Abscess
* Necrotizing Soft Tissue Infections (Necrotizing fasciitis)
* Osteomyelitis (Refractory)
* Delayed Radiation Injury (Soft Tissue and Bony Necrosis)
* Skin Grafts & Flaps (Compromised)
* Thermal Burns

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. U.S. physicians may lawfully prescribing HBOT for “off-label” conditions such as Lyme Disease, stroke and migraines. Such patients are treated in outpatient clinics. 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.

Other reported applications include:

* Diabeticaly derived illness, such as diabetic foot, diabetic retinopathy, diabetic nephropathy
* Epidural abscesses
* Certain kind of hearing loss
* Radiation-induced hemorrhagic cystitis
* Inflammatory bowel disease

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 Cochrane Library reviews.

Structure

Traditional

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:

* a pressure vessel that is generally made of steel and aluminium with the view ports (windows) or hull made of acrylic.
* one or more human entry hatches—these could be small and circular or wheel-in type hatches for patients on trolleys
* an airlock allowing human entry—a separate chamber with two hatches, one to the outside world and one to the main chamber, which can be independently pressurized to allow patients to enter or exit the main chamber while it is still pressurized
* an airlock allowing medicines, instruments and food to enter the main chamber
* glass ports or closed-circuit television allowing the technicians and medical staff outside the chamber to monitor the inside of the chamber
* an intercom allowing two-way communications inside and outside the chamber
* a carbon dioxide scrubber—consisting of a fan that passes the gas inside the chamber through a soda lime canister
* a control panel outside the chamber is used to open and close valves allowing air to enter or leave the chamber and oxygen to be supplied to oxygen helmets or masks

Oxygen breathing

Breathing 100% oxygen from an aviators’ oxygen mask.
A recompression chamber for a single diving casualty

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 patient’s 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.

Effects of Pressure

Patients inside the chamber will 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. When the patient speaks, the pitch of the voice may increase to the level that they sound like cartoon characters.

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.

Home treatment

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. Total concentration of oxygen should not exceed 25% as this can increase the risk of fire.

These chambers are often used in a clinical settings, but are also used in homes. Mild hyperbaric chambers use standard 120 volt outlets and can also be configured for 220 volt use. Ranging in size from 21″ up to 40″ in diameter these chambers measure between 84″ to 120″ in length. 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 though there is no proof that it is effective and hospitals refuse to allow their chambers to be used for this purpose. The FDA has a specific warning that supplemental oxygen is not to be used.

Treatments

Initially, HBOT was developed as a treatment for 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 then re-absorbed into the body. After elimination of bubbles, the pressure is gradually reduced back to atmospheric levels.

Protocol

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[57] (UHMS) publishes a report which compiles the latest research findings and contains information regarding the recommended duration and pressure of the longer-term conditions.

Possible complications

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[58], behind the eardrum[59][60], inside paranasal sinuses[59], or trapped underneath dental fillings[61]. 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.[62][63]

There are reports that cataract may progress following HBOT.[64] Also a rare side effect has been blindness secondary to optic neuritis (inflammation of the optic nerve).[citation needed]

Contraindications

The only absolute contraindication to hyperbaric oxygen therapy is untreated pneumothorax.[65] Also, the treatment may raise the issue of Occupational safety and health (OHS), which has been encountered by the therapist.[66][clarification needed]

Patients should not undergo HBO therapy if they are taking or have recently taken the following drugs:

* Doxorubicin (Adriamycin) – A chemotherapeutic drug.
* Disulfiram (Antabuse) – Used in the treatment of alcoholism.
* Cis-platinum – A cancer drug.
* Mafenide acetate (Sulfamylon) – Suppresses bacterial infections in burn wounds

The following are relative contraindications:

* Upper respiratory infections – These conditions can make it difficult for the patient to clear their ears, which can result in what is termed sinus squeeze.
* High fevers – In most cases the fever should be lowered before HBO treatment begins.
* Emphysema with CO2 retention – This condition can lead to pneumothorax during HBO treatment.
* History of thoracic (chest) surgery – This is rarely a problem and usually not considered a contraindication. However, there is concern that air may be trapped in lesions that were created by surgical scarring. These conditions need to be evaluated prior to considering HBO therapy.
* Malignant disease: Since cancers both thrive in blood rich environments and may be suppressed in high oxygen environments, cancer and HBO poses a dilemma since HBO both increases blood flow via angiogenesis and also raises oxygen levels. Taking an anti-angiogenic supplement may provide a solution to this problem.
* 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 reduces the risks of potential side effects.

Neuro-rehabilitation
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”.

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.

The earliest randomized, placebo-controlled, double-blind study on multiple sclerosis patients treated with HBOT suggested the therapy could improve balance and bladder function. However, by 2004 a Cochrane review assessing ten trials and 21 analyses “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.

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