Resistance to infection of transferred tissues HBO

Although the infection rate in transferred tissues is rare mainly in well blood-supplied flaps, the presence of hypoxia may often be adjacent with the insult of infection. A reduced host defense from underlying diseases also enhances and predisposes to the genesis of infection.

The results of infection can be deleterious for the compromised tissue leading to enhancement of hypoxia, dehiscence, sepsis, and necrosis. The increase of oxygen concentration has been shown to reduce the incidence of surgical-wound infection59.

The presence of oxygen is necessary for the phagocytosis and extermination of bacteria by polymorphonuclear leucocytes through the production of superoxides. Inside phagosomes membrane "oxidative burst"

includes the formation of a variety of oxidants through a NADPH oxygenase from the available oxygen.

Allen et al.60 reported that if local oxygen tension is below 30mmHg, the leucocyte bacteriocidal action is dramatically reduced; also bactericidal activity in wounds could be enhanced by three to four folds if tissue PO2 levels would raise up to 100 mmHg, as it usually happens if supplementary oxygen is provided.

Johnson et al.61 demonstrated in dogs that in composite flaps a zone of 50-75 mmHg is the most important clinically.

Leucocytes exposed to high oxygen levels after HBO application improved their phagocytic properties, even more than the relevant one in normoxic levels62.

HBO is used as an adjuvant way to surgery and antibiotic therapy to expand the therapeutic armamentarium in compromised wound healing.

Niinikoski and Hunt51 report a clinical study of surgical patients where wound infection occurred in inverse proportion to the proxy wound PO2 levels.

Anaerobic bacteria are extremely vulnerable to HBO as they lack antioxidant capacity. HBO has a bacterostatic or bactericidal effect when is used in anaerobic infections63.

Additionally aerobes are shown to be susceptible in raised oxygen's tissular levels.

Hunt et al.64 demonstrated that Pseudomonas Aeruginosa counts have been shown to decrease in animals wound chambers by inspiring high fractions of oxygen.

Knighton et al.65 showed also in animals that skin lesions from Escherichia coli, induced through dermal inoculation, varied according with inspired FiO2. Oxygen raised tension has diminished also the extension of random pattern skin flaps necrosis in dogs after their inoculation with Staphylococcus Aureus.

Furthermore experimental research66 reports possible HBO enhancement of antibiotics action due to an additive intracellular effect. Some antimicrobial agents like quinolones, macrolides, and rifampycine act within the phagocytes where an endocellular synergy between oxygen dependent reactive species and antibiotics may occur.

Regarding the above studies it is assumed that oxygen tension has a predominant role in wound's resistance to infection.

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