Hyperbaric oxygen therapy (HBO2) has many uses. The Undersea and Hyperbaric Medical Society is the international body that sets standards for the use of hyperbaric medicine. There are currently 14 approved indications for hyperbaric medicine and many more unapproved conditions where hyperbaric oxygen therapy may be useful. Hyperbaric oxygen therapy consists of placing a patient into a pressurized chamber of up to 3 atmospheres (ATM) of pressure. The surrounding ambient pressure at sea level is 1 ATM. Each additional ATM of pressure is equal to 33 feet of depth of sea water or 14.7 pounds per square inch (psi). The elevated pressure combined with exposure to 100% oxygen has many physiologic effects on the body. Many of these physiologic changes have been shown to improve wound healing in chronic wounds. This has been proven in many controlled studies. One of the most pronounced effects is the increase of oxygen concentration in the plasma. The normal oxygen concentration of plasma at sea level is 3 mL/L. At a pressure of 3 ATM breathing 100% oxygen, the plasma oxygen concentration approaches 60 mL/L. Studies have shown that this is enough to keep swine alive after all of their red blood cells have been removed and is sufficient to supply the resting oxygen requirement for most tissues. This also results in the delivery of higher oxygen concentrations to ischemic tissue. Another effect of hyperbaric oxygen therapy is decreasing surrounding edema and increasing neovascularity in ischemic tissue. Hyperbaric oxygen therapy can potentiate certain antibiotics such as aminoglycosides and quinolones. It can also be bacteriostatic and bacteriocidal at higher concentrations. Hyperbaric oxygen therapy neutralizes alpha exotoxins produced by bacteria such as Clostridium. It promotes neutrophil mediated bacterial killing ability in hypoxic tissue. Hyperbaric oxygen therapy prevents the release of proteases and free radicals in certain injuries, thereby decreasing vasoconstriction, edema, and cellular damage.