What is Hyperbaric Oxygen Therapy?

The Undersea and Hyperbaric Medical Society defines hyperbaric oxygen therapy as an intervention in which an individual breathes 100% oxygen intermittently while inside a hyperbaric chamber that is pressurized to greater than sea level pressure (1 atmosphere absolute, or ATA). For clinical purposes, the pressure must equal or exceed 1.4 ATA while breathing near 100% oxygen. 

How Hyperbaric Oxygen Therapy Works

The air we breathe has approximately 21% oxygen at 14.7 pounds of pressure per square inch (psi) when measured at sea level. In the hyperbaric chamber, the atmospheric pressure can be increased to as much as 3 times normal (about 44.1 psi), with the patient breathing 100% oxygen. This increases the amount of oxygen in the blood plasma to many times its normal levels. Higher oxygen levels are delivered to end organ tissues throughout the body and result in:

• Increased tissue oxygen concentrations, prevention of cellular death 
• Stimulation of fibroblasts and macrophages to secrete collagen and enhance neovascularization
• Reduction of capillary leakage and tissue swelling, increased tissue perfusion
• Enhancement of leukocytes bacterial killing ability
• Limited effects of ischemia-reperfusion injury

Rationale for Treatment

Hyperbaric oxygen therapy is not needed for routine, uncompromised skin grafts or flaps. However, in cases where there is decreased perfusion or frank hypoxia, hyperbaric oxygen can help maximize the viability of the compromised tissue thus reducing the need for re-grafting or repeat flap procedures. There are multiple clinical studies showing the benefit of hyperbaric oxygen for failed or failing flaps and skin grafts. Types of grafts and flaps studied include free skin grafts, pedicle flaps, random flaps, irradiated wounds and flaps, composite grafts and axial pattern flaps. Although the types of flaps and grafts are different, the common denominator to flap necrosis is tissue hypoxia. 

Hyperbaric Criteria for Treatment

• Surgical referral with diagnosis and documentation of skin graft or flap compromise (e.g., random pattern ischemia, pain, coolness or a bluish/purple hue of the cutaneous portion of flap)
• Absence of surgically correctable cause of decreased perfusion to flap or skin graft (e.g. skin flaps created by trauma with inadequate perfusion due to crush injury, large random flaps that do not follow the classic 3:1 length-to-width ratio, ischemia-reperfusion injuries, etc)

• Initiation of first HBO session within 24 hours of the initial limb/ digit replantation/ revascularization. This is generally considered a hyperbaric emergency and due consideration for urgent (within one to a few hours) initial treatment in a hyperbaric chamber.

Treatment Course

• Hyperbaric oxygen therapy at 2.0-2.5 ATA oxygen for 90 minutes. (Table 1 or Table 3)
• Hyperbaric Oxygen therapy should be started as soon as signs of flap or graft compromise appear.
• In an acutely failing flap, up to 3 treatments in the first 24 hours is recommended.
• After the first 24 hours, twice daily treatments are recommended.