Compromised Skin Grafts and Flaps
Most skin grafts and flaps in normal hosts heal well. In patients with compromised circulation, this may not be the case. Patients with diabetes or vasculopathy from another etiology and patients who have irradiated tissue are particularly subject to flap or graft compromise. In these patients, hyperbaric oxygen therapy (HBOT) has been demonstrated to be useful. [56, 57] Unfortunately, if patients are not identified early, the initial flap or graft may be lost. Even in such cases, patients can significantly benefit from HBOT to prepare the wound bed for another graft or flap procedure. The procedure then has a higher chance of success following HBOT.
Over 30 animal studies have documented efficacy of HBOT in preserving both pedicled and free flaps in multiple models. These models looked at arterial, venous, and combined insults in addition to irradiated tissues. While improvement was observed regardless of the type of vascular defect, those with arterial insufficiency and radiation injury demonstrated the greatest improvement.Human case studies documentng benefit of hyperbaric treatment for flap survival were first reported in 1966. A controlled clinical trial showing improved survival of split skin grafts followed shortly thereafter. This was corroborated by a later clinical trial. Additionally, evidence exists of benefit for flaps in post-irradiated tissue in human subjects.
As the underlying pathophysiology of all compromised grafts and flaps is hypoxia, HBOT benefits patients by reducing the oxygen deficit. A unique mechanism of action of HBOT for preserving compromised flaps is the possibility of closing arteriovenous shunts.  Additionally, the same mechanisms of action that improve wound healing, namely, improved fibroblast and collagen synthesis  and angiogenesis,  also are likely to benefit a compromised graft or flap.
The current standard for HBOT to treat a compromised graft or flap includes twice daily treatment until the graft or flap appears viable and then once per day until completely healed. The initiation of HBOT should be expedited. In general, benefit should be seen by 20 treatments. If it is not, continuation of therapy should be reviewed. However, the cost of creating a complex flap is high, which makes HBOT cost-effective for this diagnosis. Of course, patients with compromised flaps need surgical attention to the arterial and venous supply, appropriate local management, and maximization of medical support.
Adapted from https://emedicine.medscape.com/article/1464149-overview#a7