Injury or damage to tissues also results in damage and destruction of the supporting blood vessel structures. The healing process is reliant on these structures for supply of the blood containing the cells and nutrients that carry out and enable healing as well as the removal of damaged cells, debris and foreign micro-organisms. Research has demonstrated that treatment with hyperbaric oxygen therapy significantly increases the number and actual size of blood vessels in damaged tissues and wounds. This allows the healing process to occur faster speeding the recovery of the injury or wound.

Without oxygen or in a hypoxic (shortage of oxygen in the body) environment the function of white blood cells becomes diminished. This in turn provides a significant threat of infection as the bodies immune response is impaired. The increased oxygen supply offered by hyperbaric oxygen therapy assists in bacterial killing through improving leukocyte (type of white blood cell) function.

Hyperbaric oxygen therapy provides direct bactericidal (substance that kills bacteria) and bacteriostatic (hampers the growth of bacteria) effects against bacteria due to the generation of oxygen free radicals. These free radicals are able to damage the membranes and make up of the bacteria rendering them ineffective or killing them. Anaerobic (without oxygen) organisms find an increased oxygen environment toxic and are unable to survive.

Collagen is the connective tissue developed and laid down by fibroblasts, the repair cells of the body. Collagen acts as a base layer in the healing wound and assists the wound to close and repair. The formation of collagen and hence wound healing/recovery is highly dependent on the presence of adequate amounts of oxygen. The actual production of collagen by fibroblasts is also extremely dependent on oxygen availability. As hyperbaric oxygen therapy markedly increases the oxygen available within the blood this in turn enables fibroblasts to produce increased amounts of collagen required for healing of wounds and tissue damage.

Clinical research has demonstrated that a number of days following injury there occurs a migration of fibroblasts (connective tissue cells responsible for collagen production) into the area of damage. These cells then divide and replicate producing large amounts of collagen (connective tissue used to repair damage to tissue) that acts as the building block for the healing of tissue and wounds. The development and migration of fibroblasts is assisted by the influx of oxygen resulting from hyperbaric oxygen therapy, this then supports the development and action of these particular cells which play a vital part in the healing/recovery process.

With an increase in oxygen availability resulting from both blood that is highly saturated in oxygen dissolved in the plasma, and an increase in the number of blood vessels due to new vessels being created as well as the healing of damaged blood vessels, tissues and cells become highly saturated in oxygen.

The bodies initial response to any injury involves inflammation and attempted repair. Inflammation is the process by which cells such as phagocytes (white blood cells) gain access to the damaged/injured tissues and cells in order to prevent infection and enable healing to commence. Decreased oxygen supply impacts greatly upon the inflammatory process as the cells involved in inflammation are oxygen dependent. Should oxygen supply be decreased, this will greatly impair and slow the inflammatory process and healing. Increased oxygen availability promotes vasoconstriction (when blood vessels in the body become thinner) and this causes tissue fluid reabsorption and helps reduce oedema and swelling whilst keeping the tissue well oxygenated due to the high oxygen content within the blood. Hence supporting the cells of the inflammatory process to remove cell debris and micro-organisms impeding infection.

The major players in the bodies immune response are the white blood cells. Providing the body with increased oxygen availability increases the production of white blood cells providing benefit to the bodies immune response. High-dose oxygen delivered under pressures greater than sea level (hyperbaric oxygen therapy), stimulates and enables the bodies immune response.

Osteoblasts are the cells responsible for bone formation and osteoclasts are the cells responsible for bone reabsorption. Both these cells work together to form bones and control the amount of bone tissue. The provision of increased levels of oxygen allows for increased production of these cells and enables them to conduct bone repair and formation more adequately through the reduction of oedema and growth of new blood vessels in the micro-circulation.

Hyperbaric oxygen therapy mobilizes stem/progenitor cells (SPCs) by increasing the synthesis of a molecule called nitric oxide in the bone marrow. This synthesis is thought to trigger enzymes that mediate stem/progenitor cell release. Studies have demonstrated that exposure to HBOT will increase mobilization (up to 8 times) of bone-marrow-derived SPCs in humans and the number of SPCs remain elevated in blood over the course of 20 HBOT treatments. The study currently appears on-line and was scheduled for publication in the April 2006 edition of the American Journal of Physiology, Heart and Circulatory Physiology.