by Jayesh Shah, MD
Problem wounds
are those that have
failed to respond
to established
medical and surgical
management.
These wounds are usually compromised
by tissue hypoperfusion, tissue
hypoxia, and infection, and they
include diabetic foot ulcers, non-healing
postoperative wounds, non-healing
traumatic wounds, vascular insufficiency
ulcers, lymphedema wounds,
venous insufficiency wounds, and
pressure ulcers.
“Wounds with inadequate tissue oxygen
levels will not heal despite the best
wound care.” —T.K. Hunt
In the hypoxic environment of
these wounds, healing is halted by
decreased fibroblast proliferation,
diminished collagen production,
impaired capillary angiogenesis, and
the inability to control infection.
Oxygen is a drug, with many
pharmacological effects. The mechanism
by which tissues are supplied
with oxygen is via respiration of oxygen,
and subsequent delivery by
the vasculature.
There is no significant topical
absorption of oxygen. Therefore, for
additional oxygen to be delivered to
hypoxic tissues, it must be administered
systemically; in other words, it
must be breathed.
Hyperbaric oxygen therapy
(HBO2) is a treatment in which a
patient breathes 100 percent oxygen
while inside a treatment chamber at
an atmospheric pressure higher than
sea level.
Oxygen has both biochemical
and vascular effects, and HBO2 provides
intermittent correction of
wound hypoxia.
Hyperbaric oxygen therapy has
been demonstrated to have the following
effects:
• Intermittent correction of wound
hypoxia;
• Reduction of local tissue edema by
arterial vasoconstriction while
maintaining higher than normal
local oxygen delivery in wounded
tissue;
• Improved host immune response:º Improved leukocyte killing of
phagocytized bacteria;
º Direct toxic effects on anaerobic
bacteria;
º Suppression of exotoxin production;
and
º Synergism with certain antibiotics;
• Improved wound metabolism:
º Fibroblast replication and collagen
synthesis; and
º Epithelialization;
• Prevention of leukocyte mediated
post-ischemic reperfusion injury;
• Cytokine and cytokine receptor
induction:
º Angiogenesis; and
º Improved osteoclast and
osteoblast function.
HBO2 directly promotes wound
healing by restoring the oxygen
tension needed to enhance fibroblast
replication, collagen synthesis,
capillary budding, granulation tissue
formation, epithelialization, and
bacterial extermination. In so doing,
it produces granulation tissue,
increases the potential for skin grafting,
and decreases the likelihood
of amputation.
Transcutaneous oxygen (PtcO2 or
TcpO2) studies aid in assessing tissue
oxygenation. Normal TcpO2 values
are 40 mm Hg or above. TcpO2 values of less than 30 mm Hg have been correlated
with an increased risk of amputation. Low TcpO2 values may
be secondary due to hypoxia of any
cause, poor perfusion, vasoconstriction,
cigarette smoking, edema, thickened
or sclerotic skin, irradiated tissues,
probe placement over bony
structures, tendons or ligaments, and
inappropriate probe temperature.
Monoplace chambers accommodate
a single patient, and the entire
chamber is usually pressurized with
100 percent oxygen that the patient
breathes directly. Multiplace chambers
accommodate two or more patients
(and also usually an attendant or
other support personnel), and the
chamber is pressurized with compressed
air while the patients breathe
100 percent oxygen via masks, head
hoods, or endotracheal tubes.
Treatments are usually given at 2.0
to 2.5 atmospheric pressure with
diminishing returns reached by 35 to
40 treatments.
Since 1968, the Undersea and Hyperbaric Medical Society
(UHMS) has periodically reviewed the available literature on
HBO2, and it has published a list of indications for which the
data support benefit (31). HBO2 is considered the primary
treatment for decompression illness, arterial gas embolism,
and carbon monoxide poisoning (32).
As a result of the beneficial effects of HBO2 on certain conditions
that are detailed above, HBO2 also is considered a potentially
useful adjunct for a number of other conditions. The following
indications are accepted by the UHMS as adjunctive uses
of HBO2 in various wound-healing problems:
Acute thermal burns;
Clostridial myositis and myonecrosis;
Other necrotizing soft tissue infections;
Compromised skin grafts and flaps;
Crush injury, compartment syndrome, and other acute
ischemias;
Osteoradionecrosis;
Soft tissue radionecrosis;
Refractory osteomyelitis; and
Other wounds with demonstrated periwound hypoxia.
Since then, the benefits of HBO2 in wound healing have
been well-described, and hyperbaric oxygen therapy is often
part of the armamentarium of the modern “wound centers.”
Indeed, the American Board of Medical Specialties now recognizes“Undersea and Hyperbaric Medicine” as a subspecialty.
Dr. Jayesh Shah is medical director of South
Texas Wound Associates, PA and medical director
for the Center for Wound Care and Hyperbaric
Medicine at Southwest General Hospital. He is
board certified in Internal Medicine, Wound
Care, Hyperbaric Medicine, and Preventive
Medicine. Learn more about his work at
www.wounddoctors.com.
