Hyperbaric Oxygen

Alternative names: Hyperoxygenation, Adjuvant Therapy, HBO, HBOT, Hyperbarics, Therapeutic Hyperbaric Medicine.

Hyperbaric oxygen therapy (HBOT) involves the breathing of pure oxygen while in a sealed chamber that has been pressurized at 1.5 to 3 times normal atmospheric pressure.

Claims about the alternative use of HBOT include that it destroys disease-causing microorganisms, cures cancer, alleviates chronic fatigue syndrome, and decreases allergy symptoms.  A few supporters also claim that HBOT helps patients with AIDS, arthritis, sports injuries, multiple sclerosis, autism, stroke, cerebral palsy, senility, cirrhosis, Lyme disease, and gastrointestinal ulcers.  There is no scientific evidence to support these claims.  The lack of randomized clinical studies makes it hard to judge the value of HBOT for many of its claims.

History

The use of increased atmosphere pressure for medical therapy has intrigued many physicians, scientists, and lay persons for hundreds of years.  Vague accounts of increased atmosphere pressures used on humans date to the fifth century BC, and much experimentation continued from the late 1600s until the 1930s, when it fell out of favor in the medical community through lack of scientific evidence of merit.

Despite this downturn in interest, research continued and evidence of the usefulness of Hyperbaric Oxygen in areas such as wound healing grew over time.  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.

Function; Why it is Recommended

Delivery of hyperbaric pressures generally is accepted through one of two different chambers.  Monoplace chambers house one individual placed in the supine position.  Current chambers have an acrylic shell, which allows the patient to observe his or her surroundings.  Communication devices located within the chamber allow direct conversation between the patient and the hyperbaric medicine technician or physician.  Conversely, multiplace chambers can accommodate 2-10 patients.

Gas is piped directly from its source to the chamber.  Humidification and heat exchange gases are present in all modern chambers.

The application of HBO depends on the physical properties of gases under pressure, specifically, oxygen at pressure greater than 1 atm.  Oxygen is essential in a variety of enzymatic, biochemical, and physiologic interactions that promote normal cellular respiration and tissue function.  Mono-oxygenase, intradioxygenase, and interdioxygenase are specific enzymes that recruit oxygen as a cofactor to perform required biologic processes.  Collagen deposition and synthesis depend on an oxygen-dependent prolyl-hydroxylase hydroxylation of proline.  Angiogenesis and epithelization also are oxygen dependent.

Under normal conditions, 97.5% of oxygen is carried in the bloodstream bound to hemoglobin.  The remaining 2.5% is dissolved in plasma.

The effects of Hyperbaric Treatments on the cardiovascular system include decreased heart rate, decreased cardiac output, possible slight increase in blood pressure and arterial vasoconstriction after load increases.

Hyperoxygenation results in greater oxygen carrying capacity by the blood and increased oxygen diffusion in tissue fluid.  This is helpful in conditions such as severe blood loss anemia (in which the blood is unable to carry much oxygen), crush injuries, compartment syndrome graft, flap salvage and edema.

Vasoconstriction results in decreased blood flow into tissues and decreased edema; this helps with crush injuries, acute burns and compartment syndrome.

Angiogenesis results in increased oxygen supply to wounds, increased collagen deposition and the creation of new blood vessels in areas where there are not enough.  This in turn helps with graft and flap salvage, osteoradionecrosis, radiation endarteritis obliterans and healing of chronic wounds.

Fibroblast proliferation helps heal chronic wounds and treat radiation-induced injury.  Leukocyte oxidative killing leads to increased oxygen free radicals, which in turn helps with necrotizing soft-tissue infections and chronic osteomyelitis.  Toxin inhibition leads to decreased clostridial alpha toxins, helpful with clostridial gas gangrene and for decreasing cardio toxins.

Increased oxygen being transported across cell membranes helps with sepsis and necrotizing infections.

As a primary therapy, Hyperbaric Oxygen is useful for treating:

• Carbon monoxide poisoning
• Cerebral arterial gas embolus
• Decompression sickness
• Osteoradionecrosis
• Clostridial gas gangrene.

As a secondary therapy, Hyperbaric Oxygen assists with:

• Radiation tissue damage
• Osteoradionecrosis prophylaxis
• Acute ischemia and/or crush injuries
• Necrotizing infections
• Acute exceptional blood loss
• Acute thermal burns
• Compromised skin grafts or flaps
• Selected problem wounds
• Refractory osteomyelitis.

Side-Effects; Counter-Indicators and Warnings

Elemental oxygen is required to maintain cellular respiration and to allow for normal cellular protein production.  Hyperbaric medicine is considered extremely safe under appropriate supervision and utility.  Toxic effects of oxygen are observed at extremely high doses over prolonged periods.  HBO treatment increases the relative dose of oxygen; thus susceptible patients need to be recognized and modifications made to prevent the manifestations of oxygen toxicity.

Signs and symptoms of oxygen toxicity include: Nausea and vomiting, dry cough, seizures, substernal chest pain, sweating, bronchitis, pallor, shortness of breath, muscle twitching, pulmonary edema, anxiety and/or respiratory changes, pulmonary fibrosis, visual changes, tinnitus, hallucinations, vertigo, hiccups and decreased level of consciousness.

The most common barotrauma is middle ear injury.  Parts of the body that can be adversely affected by HBO treatment, with symptoms, include:

• Sinuses – Congestion and/or occlusion (Pain, bloody discharge)
• Middle ear – Eustachian tube occluded, failure to equalize pressure within middle ear space (Edema, rupture, or retraction of tympanic membrane, hemorrhage)
• External ear – Wax build-up or ear plugs occlude canal (Pain, bleeding)
• Inner ear – Oval or round window rupture (Ataxia, vertigo, tinnitus, hearing loss)
• GI tract – Gas in bowels, distention on ascent (Vomiting, nausea, flatulence, colicky pain)
• Teeth – Infected or restored teeth since they may harbor gas (Tooth pain, tooth implosion or explosion)
• Gas embolus – Extremely rare emergent decompression with blocked glottis (Sudden decreased level of consciousness; hemiplegia, blown pupil).

Do not use Hyperbaric Oxygen Therapy on patients with the following conditions, for the following reasons:

• Claustrophobia – Anxiety
• Pneumothorax – Gas emboli, pneumomediastinum, pneumoperitoneum tension (pneumothorax), subcutaneous emphysema
• A history of spontaneous pneumothorax – Increased lung bleb incidence (pneumothorax)
• Chronic obstructive pulmonary disease (COPD) – Increased oxygen intolerance, increased risk of seizures
• Pneumocystis carinii pneumonia – Questionable fetal teratogen
• Seizure disorders – Barotrauma to sinus/ear/lung
• Pregnancy – Decreased threshold for oxygen-induced seizures (although HBO therapy may be required in pregnancy in situations of carbon monoxide poisoning, cerebral gas embolus, decompression sickness, or clostridial myonecrosis.)
• Upper respiratory infection – Increased hemolysis
• Hyperthermia
• Hereditary spherocytosis
• Optic neuritis – Possible increased optic nerve pathology
• Malignant tumors – possible increased vascularity for tumors
• Acidosis – Decreased threshold for oxygen seizures
• Steroid use – Decreased threshold for oxygen seizure
• Alcohol use – Dehydration (increased risk of decompression sickness)
• Nicotine use – Decreased seizure threshold.