"Hyperbaric oxygen therapy (HBO2T) is neither necessary nor recommended for the support of normal, uncompromised grafts or flaps. However, in tissue compromised by irradiation or in other cases where there is decreased perfusion or hypoxia, HBO2T has been shown to be extremely useful in flap salvage. Hyperbaric oxygen can help maximize the viability of the compromised tissue thereby reducing the need for regrafting or repeat flap procedures".
This is the official stance of the Society of Undersea and Hyperbaric Medicine which is the international organization that sets standards for indications and implementation of hyperbaric medicine.
A skin graft or flap involves transferring healthy skin, either full thickness or partial thickness, to a denuded area of the body to aid in healing. There are free-transfer grafts where skin, usually partial thickness, is removed from one area and placed at a more distant site, and there are rotation flaps. Rotation flaps are done by surgically freeing a full thickness amount of skin and rotating it to a nearby location. This involves preserving the native blood supply. Care must be taken with these graft so as not to compromise this native blood supply either from undue tension or torsion of the pedicle. Hyperbaric medicine has been shown to be useful in improving healing and providing higher success rates in compromised grafts and flaps. Hyperbaric oxygen therapy has several effects that are beneficial for healing these compromised grafts. It has been proven that HBO2 therapy will increase the oxygen carrying capacity of plasma up to 7%. This has been shown to be adequate to keep swine alive after all of their red blood cells have been removed. Hyperbaric oxygen therapy will result in increasing neovascularization and decrease tissue edema. This combination will improve the tissue environment in areas of vascular compromise. Hyperbaric oxygen effects are also advantageous in situations of crush injuries with grafts. These situations result in large amounts of edema, compromising any grafts done in these locations. Burn patients often require skin grafting. The burn setting presents with several complex processes that can compromise graft healing. Burns cause a hypercoagulable state in the microvascular. This will impede oxygen supply to these areas. HBO2 therapy increases neovascularization, thus improving blood supply to compromised areas. The increased oxygen-carrying capacity of the plasma will also aid in decreasing destruction of borderline tissues as time progresses. Localized edema is decreased with HBO2 therapy, which decreases tissue pressure and increases microvascular blood flow. Burn patients are susceptible to infections. HBO2 therapy helps lower infection rates by oxygen's bacteriostatic and bacteriocidal effect on certain microorganisms. Higher tissue oxygen content also neutralizes exotoxins. 
Free, partial-thickness skin grafts are reliant on the local accepting tissue and its microvasculature. Neovascularization is essential for acceptance of the donor tissue. Full-thickness rotation flaps are dependent on the main intact vasculature of the transfer area's pedicle.
There is no indication for hyperbaric oxygen therapy in uncompromised flaps and grafts. Situations, where HBO2 therapy is approved for skin grafts and flaps, includes various settings where there is a vascular compromise. Areas of past radiation exposure result in decreased micro vascularization and overall poor tissue conditions. Reperfusion injuries such as with crush injuries have shown to benefit from HBO2 therapy. Thermal burns with skin grafts are also indications for HBO2 therapy. 
Most contraindications to hyperbaric oxygen therapy are related to issues of barotrauma. This is when there is physical injury to an area where there is a closed air-filled space such as the lung or middle ear. Injury results from expansion of trapped gases with the changing pressure from the hyperbaric dive resulting in rupture of the compartment (perforation of a tympanic membrane or pneumothorax). The only true absolute contraindication is an untreated pneumothorax. Diving a patient in this situation will lead to fast progression of a tension pneumothorax and certain death. More relative contraindications are the presence of pulmonary blebs and emphysema with carbon dioxide retention. Administration of certain drugs is a relative contraindication. Disulfiram blocks superoxide dismutase which protects against oxygen toxicity (a known risk of hyperbaric oxygen therapy). Cisplatinum and sulfamylon impair wound healing. Bleomycin can cause interstitial pneumonitis. Sinusitis, seizures, pregnancy, and implanted devices such as pacemakers and epidural pumps are also relative contraindications. Claustrophobia, especially in cases of the monoplace chamber, can be an issue.
Hyperbaric oxygen therapy is administered in an approved and inspected the pressurized chamber. The chambers are either monoplace chambers which hold only one patient at a time or multiplace chambers which can accommodate several patients and an overseeing physician.
The multiplace chambers can accommodate a wider variety of patients such as those on ventilators or those who need special accessory equipment that would not fit into a monoplace chamber. This activity regulates everything from the exhaust carbon dioxide to the purity of the oxygen and air. Frequent inspections are mandated, and the staff has to be specially trained to oversee hyperbaric dives. There is also a safety director appointed to each facility ensuring compliance with specifications. The most catastrophic event associated with a hyperbaric dive is a failure of the chamber or fire. Hopefully, the frequent inspections and keen vigilance of the staff will avoid failure of the chamber. Fire prevention is also at the forefront of concern with dives. Three things are needed for a fire; a combustible material, a spark or fire source, and oxygen. Patients are limited to what they can bring into the chamber. No oils, electronics, or other non-approved items are allowed. They must wear only specially approved gowns, and no street clothes are permitted. Patients are also grounded to prevent static sparks. Any non-approved electronic equipment can only be used away from the open chamber. 
The physicians and all personnel including the cleaning staff must have special training in hyperbaric medicine and the chambers. Each overseeing physician must complete at least a 40-hour training course in hyperbaric medicine. Physicians can also get certified in undersea and hyperbaric medicine through a year-long fellowship. Hyperbaric techs must also take a 40-hour hyperbaric course. There is an appointed safety officer who has extra safety and maintenance training. Cleaning personnel must be aware of precautions needed to clean the acrylic monoplace chambers and the other special details in caring for and maintaining multiplace chambers.
Hyperbaric dives follow specific proven dive protocols depending on the condition being treated. Dives last 2 hours daily with two, 10-minute oxygen breaks to prevent oxygen seizures. They usually go to a pressure of 2.4 ATM at 100% oxygen. A typical dive routine lasts for 30 sessions but can be extended if it is felt to be beneficial. 
The most common complication of hyperbaric oxygen therapy is barotrauma. Barotrauma is caused by the expansion of gases in a confined space. The most common barotrauma is rupture or irritation of the tympanic membrane. Other more serious injuries include pneumothorax, rupture of small vessels, and damage to the inner, middle and external ear canals. More serious hazards include oxygen seizures, convulsions, and pulmonary edema and hemorrhage. Catastrophic complications are chamber fires and explosions.
Not all failed or compromised flaps or grafts respond to hyperbaric oxygen therapy. Prolonged treatments may be required. Loss of the flap or graft is a possibility that could require extensive debridement with loss of skin coverage. This could significantly increase patients' morbidity and mortality. 
Awareness of possible compromise or impending compromise of skin grafts and flaps is essential. Early initiation of hyperbaric oxygen therapy in these situations may lead to better results. 
Hyperbaric oxygen therapy has many uses. It is indicated for certain soft tissue conditions including compromised and ischemic skin grafts. The treating surgeon and wound care specialist must be aware of these indications in order to make the appropriate and timely referral for hyperbaric therapy. This will add to a better outcome and flap salvage for a certain percentage of patients who would otherwise be victims of failed grafts and poor outcomes.