Hyperbaric Oxygen Therapy

 

Hyperbaric Oxygen Therapy

PKGhatak,MD

 

In any coastal community where scuba diving activities and commercial sea diving are common, one can find at least one Hyperbaric Oxygen Treatment Center.

Caisson disease, commonly called Bends is an episodic arterial obstruction from Gas bubbles formation due to the release of dissolved Nitrogen and Oxygen in the blood during rapid ascent from a deep dive.

Bends also happen to passengers of an airplane, if the aircraft suddenly loses cabin pressure at an altitude of 35,000 feet or higher. Fighter pilots and submarine sailors are at risk of having bends.

Both nitrogen and oxygen are poorly soluble in blood. In blood, almost all Oxygen (O2) is carried as loosely bound oxyhemoglobin in the RBCs. 1.34 ml of O2 is bound to per 1gram of hemoglobin. O2 is prevented from forming the oxidation of ferrous iron of hemoglobin in the RBC due to the presence of antioxidants and respiratory enzymes. In normal conditions, the O2-carrying-capacity of hemoglobin is 98 to 99% saturated. Increasing either O2 concentration or pressure or both cannot increase O2 saturation any further. Only about 0.3 ml of dissolved O2 is present in 100 ml of blood. Fatty tissues contain most of the dissolved nitrogen (N2).

At one atmospheric pressure and breathing room air, the dissolved O2 is 0.3 ml/dL. When breathing 100% O2, the dissolved O2 increases to 1.5 ml/dL; at a pressure of 3 Bar, the dissolved O2 is 6ml/dL. That much of dissolved O2 is sufficient to supply all the O2 requirements of tissues and then some more.

Characteristics of dissolved O2.

Tissues in the tiny places where capillaries cannot reach and specially in areas where blood vessels are blocked due to infection or diseases, the dissolved O2 easily diffuses out of the blood into the cells. In an O2 rich environment, anaerobic bacteria cannot survive. Phagocytic activities of leukocytes increase due to enhanced peroxide actions. Fibroblast proliferation is enhanced and promotes tissue repair. High O2 generates new blood vessels and is called angiogenesis. Blood vessels are constricted in high PaO2, and that property is utilized in the treatment of thermal burns and crush injuries.

Adverse effects of high O2 environment.

O2 toxicity of the lungs may produce pneumonitis and pulmonary fibrosis. The opacity of eye lenses may develop. Various neurological symptoms including seizures may happen. Retinal changes produce various symptoms but are amenable to treatment.

Adverse Pressure effects.

Pain over nasal sinuses, pain in the inner ear and occasional rupture of eardrums may happen. Temporary vision changes are seen from deformity of the eye lens. Toothaches from the pressure effect of filled cavities are not uncommon.

HBO therapy in Bends.

At 3 Bar pressure and breathing 100% O2, the gas bubbles dissolve back in the plasma. As blood travels to the lungs the dissolved gases diffuse out from blood to the alveolar sacs and are expelled during exhalation. Generally, one treatment of HBO lasts about 4 hrs. with 20-minute break every 2 hrs. in order to minimize O2 toxicity. For the treatment of Bends usually, two sessions are required for the completion of the removal of all dissolved N2.

Various types of Hyperbaric O2 apparatus.

HBO chambers of various sizes are available to accommodate single patients to multiple patients. For the treatment of the localized area of limbs, head-neck and trunk, equipment of various shapes and sizes is available. The body part to be treated is hermetically sealed with inflatable cuffs and has ports for oxygen and other agents. To minimize tourniquet effects on the tissues, the pressure is released periodically.

Indication for HBO therapy.

Besides caisson disease, air embolism is at the top of the list. Other medical conditions are gas gangrene, diabetic foot ulcers, thermal burns, anaerobic resistant infection of the skin and subcutaneous tissues, poorly healing surgical wounds and skin flaps and grafts, resistant osteomyelitis and osteonecrosis, crush injuries, acute hemorrhage in people unwilling to accept blood transfusion because of religious belief. Hard to reach intracranial abscesses, and less well defined circumstances.

Hyperbaric oxygen therapy is a lifesaving treatment device for well-defined conditions and also in the field of experimentation.

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