Raising the Bar

Hyperbaric or high-pressure therapy without oxygen dates back to 1662, when it was used unsuccessfully to treat rickets, scurvy, and arthritis. A century after the discovery of oxygen in 1775, it was combined with pressure to study its effects on experimental animals. Oxygen toxicity became readily apparent as seizures and pulmonary damage occurred.

Beginning in 1937, hyperbaric oxygen was used to treat divers who spent too much time underwater and surfaced too rapidly. A 1966 coal mine disaster in Japan ushered in the wound-healing era of HBOT. Miners with thermal burns and carbon monoxide poisoning were treated in an HBOT chamber, and their skin healed significantly better than those treated conventionally.

Through the 1960s, HBOT was applied to a multitude of unrelated chronic ailments. The lack of proven efficacy of HBOT for these conditions resulted in a backlash of skepticism against this treatment modality.

Finally, in 1976, the Undersea and Hyperbaric Medical Society developed a list of scientifically proven indications for HBOT:

1. Air or gas embolism
2. Carbon monoxide or cyanide poisoning
3. Clostridial myositis and myonecrosis (gas gangrene)
4. Crush injury, compartment syndrome, acute traumatic ischemias
5. Decompression sickness (bends)
6. Arterial insufficiencies (retinal artery occlusion, diabetic foot ulcers)
7. Severe anemia
8. Intracranial abscess
9. Necrotizing soft tissue infections
10. Chronic refractory osteomyelitis
11. Delayed radiation injury
12. Compromised skin grafts and flaps
13. Acute thermal burn injury

Medical indications for HBOT have expanded in recent decades. In the United States, the number of hyperbaric oxygen chambers has grown from 37 in 1977 to more than 800 today.

Treatment consists of placing the patient in a specially designed clear plastic pressure chamber. Once the chamber’s hatch is closed, the patient breathes 100% oxygen at twice normal atmospheric pressure. Because of the risk of fire, the patient is dressed in a plain cotton gown, and takes nothing into the chamber except a bottle of drinking water. A grounding strap is worn on the wrist to prevent the building of static electricity and a spark. Hearing aids, dentures, and medication patches are all removed before the treatment, which normally lasts two hours. A course of therapy typically requires 30 “dives” over a period of six weeks, though acute conditions (thermal burns, compromised grafts, or carbon monoxide poisoning) may need just a few.

Under normal atmospheric conditions, oxygen is simply a requirement of metabolism. At higher pressures and concentrations, its physiologic effects increase. For example, in a patient with bends, gas embolism, or gas gangrene, high-pressure oxygen compresses the gas bubbles trapped in capillaries and tissues, restoring normal blood flow. At three times atmospheric pressure, sufficient oxygen is dissolved in plasma that the body’s resting metabolic needs can be met without hemoglobin. Failing grafts and skin flaps, severe anemia, and vascular insufficiency all respond to this mechanism of action.

Vasoconstriction caused by HBOT reduces capillary hydrostatic pressure and edema in crush injury and compartment syndrome. High oxygen concentration allows this metabolite to diffuse farther outside capillaries spread apart by edema fluid, thus reaching hypoxic cells. High oxygen gradients stimulate new growth of blood vessels to help heal diabetic foot ulcers and radiation damaged tissue. Even brief exposure to hyperbaric oxygen causes fibroblasts to increase collagen production to create the framework for reconstruction.

HBOT doubles the killing power of hypoxic white blood cells. This process inhibits anaerobic bacteria, suppresses exotoxins and destroys some clostridia and cytolytic toxins. Transport of certain antibiotics across bacterial cell walls is also enhanced, causing these drugs to work more efficiently. In addition, intracranial abscesses, invasive mycoses, and chronic foot ulcers can respond to the anti-infective mechanisms of HBOT.

HBOT’s numerous benefits do not come without risks. Pressure changes can injure the middle and inner ear as trapped air contracts and expands. Barotraumas can also create or worsen pnemothorax, cause sinus pain, and damage certain older implanted devices such as pacemakers. Some patients experience confinement anxiety, or claustrophobia, during the first few treatments. This symptom can be alleviated with emotional support, reassurance, or medication. Diabetic patients can become hypoglycemic with HBOT, as glucose uptake by muscle cells accelerates. These individuals must test with a pretreatment blood sugar of at least 120 before entering the chamber. Oxygen toxicity causes seizures once in every 10,000 exposures, even in patients who have successfully completed previous treatments. Paresthesias occur commonly, but resolve after therapy is completed. Pulmonary toxicity is rare in the outpatient setting, but alveolar edema, hyaline membrane formation, and interstitial fibrosis can occur with more intensive regimens. Existing cataracts can be worsened by HBOT, but treatment does not typically cause new cataracts if the treatment regimen is fifty applications or fewer. One-third of patients will become temporarily nearsighted after two weeks of treatments, but this symptom resolves spontaneously within several months.

Some patients are excluded from HBOT. Untreated pneumothorax or a history of spontaneous pneumothorax are absolute contraindications. Any prior bleomycin treatment creates a risk of interstitial pneumonitis. Recent administration of cisplatin, carboplatin, or doxorubicin requires postponement of therapy. Disulfiram (Antabuse) and mefanide (Sulfamylon) increase the risk of oxygen toxicity seizures. Relative contraindications include seizure disorders, high fever, severe COPD, CHF, and history of thoracic surgery, although most of these can be managed though a course of treatment.

HBOT is expensive – a course of 30 outpatient treatments can cost $40,000 or more. Despite the cost, HBOT is life-saving and limb-saving therapy. Prospective, randomized controlled trials demonstrate a 75% reduction in major amputations for advanced diabetic foot ulcers. HBOT is the only effective treatment for delayed radiation injury disease. Medicare, Medicaid, and most major insurance carriers cover the list of indications approved by the Undersea and Hyperbaric Medical Society.

Standard wound care, not HBOT, is still the mainstay for 85% of patients who present to Northern California Wound Care and Hyperbarics. This hospital-based, physician-directed program employs a multidisciplinary team to treat diabetic ulcers, delayed radiation injury, arterial and venous ulcers, chronic osteomyelitis, thermal burns, failing grafts, and other problem wounds. The medical professionals at Northern California Wound Care and Hyperbarics provide meticulous attention to circulation, debridement, infection control, wound bed moisture, mechanical protection, compression, neuropathy, and malignancy. Referrals from physicians, nurses, institutions, and patients themselves are accepted.