HBOT AND COMPROMISED SKIN GRAFTS AND FLAPS

Although hyperbaric oxygen therapy is not the first modality of treating routine
complications of skin grafts, it is considered an appropriate adjunctive treatment
modality in selected patients. In areas of impaired circulation, HBOT preserves
tissue viability. Tissue oxygen tensions of 4-6 kPa (30 to 40 mmHg) are required for
fibroblast regeneration and normal wound healing. Collagen deposition serves
as a matrix to support new blood vessel growth (neovascularization). New capillary
buds start to be noticeable within 5 to 10 days of daily hyperbaric oxygen therapy
and a rich vascular bed is established within one month. In a compromised host
or patient with marginal circulation, hyperbaric oxygen therapy will improve the
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granulation base and may permit “take” of a graft that would otherwise fail. HBOT is
also useful in treating flaps which have a hypovascular base. Using animals, HBO2
has been demonstrated to preserve flap length compared to non-treated control
animals. HBOT may even have direct effects not dependent on the circulation.
Using a pig model, Tan et al, raised skin flaps designed to become ischemic. After
killing the pigs, their carcasses were placed in a chamber. The flaps still responded
and became pink! They conclude that, in the absence of circulation, this could only
be explained by the flaps’ direct absorption of oxygen from the chamber air. Li et al
experimented on auricular composite grafts in rabbits treated with HBOT They
suggest that HBOT enhanced graft survival, especially in the larger composite grafts.
In compromised flaps the contributing factors include hypoxia, edema, arterial
vasospasm, arterial or venous occlusion, congestion and dehiscence or infection.
Another factor of major importance is the so-called “reperfusion injury syndrome”
when re-establishment of circulation follows prolonged tissular hypoxia as in
complicated free flaps. Patient health factors like age, smoking, systemic disease
and/or relative therapy may interfere with the flap prognosis. Clinical evaluation is of
major importance and is tested according to the flap condition taking into account
flaps characteristics like color, temperature, capillary fill and bleeding. The
appearance of cyanotic colour in a graft is associated with delayed revascularization
and hypoxia, white color with lack of blood supply and red color with presence of
infection. Follow up of the flap “take” is critical for the first 48 hrs. Observation of
the flap color may determine the leading factor of the complication. The primary
cause of flap demise is not an inadequate arterial inflow but rather a venous
insufficiency through a compromise venous outflow.
If a surgical flap is clinically edematous, with a deep purple or dark blue colour, (i.e.
in total venous occlusion), capillary refill is missing and the flap temperature is low,
then HBO2 is recommended , whether preparing a site for
grafting, or maximizing survival of a new graft.