Binding of CO to the haemoglobin molecule to form carboxyhaemoglobin, reducing oxygen delivery to the tissues. Undefined cellular effects, as well as lipid peroxidation and cytochrome binding.

• Produces a rapid dissociation of CO from haemoglobin (the half-time for elimination of CO is reduced from over 5 hours with air to 23 minutes).
• Oxygen breathing at 3 atmospheres absolute (ATA) provides immediate delivery of dissolved oxygen in plasma in an adequate amount to support basic tissue metabolism, even when the amount of CO bound to haemoglobin is high.

1. Crush injury is a diffuse traumatic injury involving two or more tissues with a gradient of injury and compromised blood supply. The primary insult is tissue ischemia and cellular hypoxia. Secondary effects of vasodilation at the pre-injury level lead to increased oedema and further vascular compromise thus compromising the tissue's ability to handle infections.

Optimal response is evident if treatment is initiated within six hours of injury. Results are variable and are dependent on time to intervention. A literature review revealed benefit in approximately 60% of cases resulting in increased extremity survival, decreased tissue loss, and amputation at a more distal level.

• Increases oxygen tension leading to greater capillary oxygen diffusion distances.
• Produces a vasoconstriction that reduces oedema formation.
• Has an indirect effect of leukocyte enhancement and increased wound healing.
• Decreases neutrophile adhesion & activation in the ischemic-reperfused tissue.

Abscess formation in the brain can be a devastating complication of sinus infections or bone infections (osteomyelitis) of the skull. Occasionally, abscesses start from an infection from other parts of the body. Abscesses in the brain frequently occur in multiples. One of the problems in the treatment of brain abscesses is that surgical drainage of the abscesses is often required for cure. Unfortunately, normal brain tissue surrounding the abscess may be unavoidably damaged by such surgery. Fine needle aspiration of the abscesses is being performed with greater frequency to avoid this problem.

Antibiotics are used for treatment, but they may not penetrate well into brain abscesses. Furthermore, white blood cells, which kill infecting bacteria, may not have enough oxygen to effectively eliminate the infection if they are functioning deep in the abscess at a distance from their normal blood supply. White blood cells require a minimum level of oxygen to kill bacteria.

Most intracranial abscesses are caused by anaerobic bacteria (bacteria that function optimally in low oxygen concentrations). Hyperbaric oxygen therapy raises the oxygen level in the region of the abscess, exposing the bacteria to levels which may inhibit or kill them, as well as providing sufficient oxygen for white blood cells to exercise their killing power.

The average mortality rate from intracranial abscess reported in six large studies was 20 percent when hyperbaric oxygen was not used. Among the 48 known cases treated with hyperbaric oxygen to date, the mortality rate has been only 2 percent. Additionally, most of the patients treated with hyperbaric oxygen have returned to their regular daily activity after recovery, with less apparent brain damage. Therapy with hyperbaric oxygen carries minimal risks.

Skin grafts and compromised skin flaps represent a classical problem involving insufficient oxygen supply to tissue. Plastic surgeons use the grafts and flaps to repair serious damage, and to close or cover wounds. Skin is taken from one part of the patients, body and used to cover a break in the skin on another part. There are several types of skin grafts. They include Full-thickness grafts, in which all of the skin layers are used, and split-thickness grafts, in which only the top layers and several of the deeper layers are used. There are also pedicle grafts, in which part of the skin remains attached to the donor site. This allows the old blood supply to remain intact while a new blood supply develops.

The problem is what to do when skin grafts appear not to be taking. A freshly applied split-thickness graft receives no oxygen until tiny blood vessels called capillaries can penetrate into it. Such capillary ingrowth normally takes place over a two to three day period. If this does not happen, it's not likely that the graft will survive. HBOT improves the chances that a graft will take, both by supplying oxygen and by encouraging quick capillary growth.

Providing hyperoxygenation increases the oxygen tension in the graft bed and wound margins up to 1500 percent. In turn, the hyperoxygenation causes a marked increase in the effectiveness of the blood or plasma that reaches the graft through compromised blood vessels. The volume of tissue that derives sufficient oxygen from a single damaged blood vessel increases 16 fold, and marked tissue salvage results.

Lack of oxygen tends to be less of a problem with full-thickness and pedicle grafts since these grafts have their own supply of capillaries. Even so, it still takes time for good blood flow to become established through these type of grafts, Therefore, full-thickness and pedicle grafts also respond to HBOT. In the case of pedicle graft, it is important that HBOT be employed before what little circulation that is present develops blood clots.

In many instances HBOT is used only after a skin graft starts to fail. While HBOT can help save failing grafts it can be even more effective when used before surgery to keep grafts from failing in the first place.

HBOT also offers strategies for reducing oedema. The oedema reduction effect, induced by the relative spasm of a precapillary arteriolar sphincter helps to limit the swelling of the graft or flap. The high oxygen tension achievable with HBOT induces large oxygen neovascularization. Among other things, oxygen dissolved in plasma is readily available to tissues and organs thus limiting damage from reperfusion injury.

HBOT's effectiveness in aiding skin graft survival is supported by research. The effectiveness of HBOT is shown in grafting and in reimplantation of limbs, with a salvage rate of 75% for the HBOT group compared to 46% for the controls, with 100% HBOT salvage when the patient is treated within 72 hours post-operatively.

The use of HBOT for the preparation of a base for skin grafting and the preservation of compromised skin grafts has been well documented as effective.

Refractory osteomyelitis is a bone infection which has not responded to appropriate treatment. Hyperbaric oxygen increases the oxygen concentration in infected tissues including bone and kills or inhibits the growth of organisms which prefer low oxygen concentrations. These effects occur through the oxygen-induced production of toxic radicals or through an indirect effect medicated through the white blood cells (polymorphonuclear leukocytes).

Thermal burn injuries, if not fatal, can cause disastrous long-term physical and emotional disability for the survivor. Especially in closed space fires, thermal and smoke (products of combustion) damage to the lungs can occur requiring in some cases intubation and use of a mechanical ventilator.

Burn injuries characteristically progress to become deeper and more extensive with time. Peak damage occurs within 3-4 days after the initial burn, and can be up to 10 times worse than the initial burn injury. In more severe and/or extensive burns (deep second, third and fourth degree burns), multiple aggressive surgeries are generally necessary to excise the burned tissue and later to perform skin grafts to cover these areas.

Burn injuries can result in lifelong difficulties, physical limitations, loss of job and employment opportunities and significant disfigurement as the body heals from the injury. In many cases the burn victim's life is radically changed literally overnight and the psychiatric adjustments can be overwhelming. When possible, these injuries should be treated in centers that specialise in the management of thermal burns.

Adjunctive hyperbaric oxygen (HBO2) therapy has been shown to limit the progression of the burn injury, reduce swelling, reduce the need for surgery, diminish lung damage, shorten hospitalisation and result in significant overall cost savings. These benefits are more apparent if therapy is initiated within 6-24 hours of the burn injury.

Ideally, the patient should have 3 sessions in the first 24 hours, twice daily treatments until the process stabilizes, then continued therapy as indicated for healing enhancement and to support grafted areas. Indications for HBO2 therapy typically include deep second-degree and third-degree burns that involve greater than 20% of the total body surface area, and less extensive burns that involve the face, hands or groin area. Best results are realised when HBO2 is used as an integral part of an aggressive multidisciplinary approach to the management of this potentially fatal injury. HBO2 is a very safe therapy even in seriously injured patients when administered by those thoroughly trained in HBO2 therapy in the critical care setting and with appropriate monitoring precautions.