HYPERBARIC OXYGEN
Definition
treatment during which a patient breathes 100% oxygen inside a closed chamber pressurized above 1
atmosphere absolute (ATA).
Physiology

At 1 ATA, the oxygen in blood is almost entirely carried by hemoglobin. Because hemoglobin is
approximately 97% saturated under normal conditions, greatly increasing the oxygen-carrying capacity of
blood by increasing hemoglobin saturation is not possible.

At 3 ATA and 100% O2, 60ml/L of O2 dissolved in blood. ie can supply tissue O2 requirement without
use of Hb.

The difference in the partial pressure of oxygen from the arterial side to the venous side of the capillary
system is approximately 37 times greater when breathing 100% oxygen at 3 ATA than air at 1 ATA.

Oxygen diffusion levels during HBO inhalation are at least 2 times the values obtained during normobaric
oxygenation.
Effects
1) increased delivery of oxygen to tissues. Fibroblast synthesis of collagen requires tissue oxygen
tensions of 30-40 mm Hg. HBO therapy has the potential to achieve these levels in hypoxic or poorly
perfused tissues. The collagen matrix created by fibroblasts is essential for neovascularization by
capillary ingrowth. In radiated tissue, HBO has been shown to be more effective than normobaric
oxygen in increasing the partial pressure of oxygen in tissue.
2) vasoconstriction. Hyperoxia causes a rapid and significant vasoconstrictive effect. Vasoconstriction
occurs without a significant reduction in tissue oxygenation and can be used to reduce tissue edema in
skin flaps and grafts.
3) Antibacterial - HBO alone is bactericidal to strictly anaerobic organisms. HBO is bacteriostatic to
many microaerophilic organisms and some species of Escherichia and Pseudomonas. Oxygen
concentrations can alter antibiotic activity. Antibiotics such as trimethoprim/sulfamethoxazole,
aminoglycosides, and quinolones have been shown to be less active in an anaerobic environment.
Other antibacterial effects of HBO involve toxin inhibition or deactivation
USE IN PLASTIC SURGERY

Use in plastic surgery is as an adjunct and never as primary modality
Infection

HBO has direct and indirect bacteriostatic and bacteriocidal effect
1) Direct
a. Oxidise proteins and membrane lipids
b. Damage DNA and inhibit metabolic functions
c. Directly toxic to strict anaerobes
d. bacteriostatic to many microaerophilic organisms and some species of Escherichia and
Pseudomonas.
e. Suppresses -toxin of Clostridia perfringens
f. Increases effect of certain antibiotics – Gentamicin, quinolones, Bactrim
2) Indirect
a. Improved leukocyte function - Impaired when PO2 <30mm Hg

Indications
1. Clostridial myonecrosis

Obligate anaerobe

mainstay of treatment for clostridial myonecrosis remains surgical debridement, antibiotic
therapy, and treatment of shock.

standard treatment should not be delayed while access to HBO therapy is arranged.
2. Necrotising infection/Fournier’s gangrene

Surgery + ABs + HBO do best

The addition of HBO therapy to a treatment regimen of surgery and antibiotics in
experimentally induced clostridial myonecrosis in dogs significantly increased the survival
rates from 70% to 95%
3. Refractory osteomyelitis

Neovascularization of the bone is hypothesized to account for long-term remissions that
seem to be more common in patients treated with HBO. Clinical data are limited.
Wound Healing

Collagen formation is O2 dependent; Increases substrate

HBO may be advantageous if a skin graft is placed in an irradiated field or where the microcirculation is
known to be compromised. Animal studies have demonstrated enhanced flap and graft survival with the
addition of HBO therapy to postoperative care. A few clinical studies have also demonstrated that HBO
enhances graft and flap survival in patients with ischemic flaps and grafts

Two studies, dealing with two different procedures- myocutaneous flaps and split skin grafts: Both
showed benefit (increased graft survival, reduced infection and and flap dehiscence) but studies were
poorly described and designed.

Potential for use with diabetic ulcers. Major amputations less likely in those who received HBO.
Crush Injury

One study looking into patients with Gustillo Type II or III acute injury of the lower limb.

statistically significantly greater proportion of HBOT subjects experienced complete healing of lesions
(reduction in surgical procedures) without necrosis compared to those given the placebo therapy.
Osteoradionecrosis

Produces progressive obliterative endarteritis ie hypocellular, hypovascular and hypoxic tissue

HBO promotes angiogenesis and fibroplasia

Benefit with dental extractions in XRT mandible (Miami protocol 30/10 dives)
Thermal Burns

Exposure to HBO was not shown to improve mortality in studies that examined this outcome

Overall, there is little firm evidence and a lack of well-conducted studies to support the use of hyperbaric
oxygen therapy for thermal burns.
Contraindications
Absolute
1. untreated pneumothorax (tension)
Relative
1. pregnancy
2. seizure disorder (lowers seizure threshold)
3. claustrophobia
4. malignancy – questionable (increased vascularity for tumors)
5. chronic obstructive airways disease
Complications
1. Barotrauma
a. Middle ear - can be treated by the placement of grommets
2. Eyes
a. Reversible myopia is most common (up to 50%)
b. Retrolental fibroplasia - characterized by abnormal retinal vasculature and varying degrees of
visual impairment. It occurs in premature infants exposed to high postnatal oxygen
concentrations but has not been reported in adults.
c. Cataracts
3. Acute central nervous system oxygen toxicity
a. a rare complication.
b. estimated to occur in 1 in 11,000 treatments.
c. In most people, exposure to 100% oxygen at 3 ATA for 3 hours induces grand mal seizures.
At less than 3 ATA, seizures are rare.