What Is Hyperbaric Oxygen Therapy?
Although hyperbaric oxygen therapy has its place in smoke inhalation, carbon monoxide poisoning, and diving complications, its role in wound healing centers on correcting hypoxia to tissues compromised by trauma, infection, or the elements.
The physics of hyperbaric oxygen therapy is based on gas dissolving into solutions proportionately with its pressure. Delivering oxygen under pressure augments the oxygen content in the tissue, thereby addressing acute or chronic ischemia. This is an important advantage in wound healing.
Hyperbaric oxygen therapy is an adjunctive therapy for acute traumatic and ischemic injuries, such as crush injuries, compartment syndromes, and situations of vascular compromise.
It increases the survival of skin grafts and reconstructive flaps that have compromised blood flow. This prevents tissue breakdown by improving local vascularity. Previous graft failure sites benefit from prophylactic hyperbaric therapy.
Once hyperbaric oxygen therapy raises the amount of oxygen in tissues in the healing process, the effects of injury, ischemia, and inflammation are diminished. These damaging effects are mediated by oxygen free radicals and hydrogen and nitrogen split-products which are all mitigated by the augmentation of oxygen saturation. This hyperoxia causes vasoconstriction to reduce edema, limits leukocyte (white blood cell) influx, helps fibroblast proliferation, and promotes neovascularization (new blood vessels) that enhance the healing process. It also has antimicrobial effects.
Hyperbaric chambers are designed to accommodate either one person or more than one. The only absolute contraindication to a hyperbaric chamber is pneumothorax. Relative contraindications include severe COPD. Pregnancy is not a contraindication.
- Middle ear trauma, more common in those undergoing multiple treatments. Rupture of the eardrum is possible, but rare.
- Sinus trauma due to the pressure, which occurs in those with upper respiratory infections.
- Pulmonary trauma, unusual; it is accompanied by pulmonary edema.
- Pulmonary toxicity: chest tightness, cough, and reversible pulmonary function impairment.
- Rare seizures due to nervous system oxygen toxicity is more of a risk in those exposed to >90-120 minutes or >2.8 atmospheres.
What Testing Is Needed for Hyperbaric Oxygen Therapy?
For any wound healing, the wound bed has to be well-vascularized. Hyperbaric oxygen therapy (HBO) is closely tied to oxygenation of tissues via perfusion and blood supply to those tissues. Testing for vascular compromise is part of the protocol for assessing a patient’s candidacy for HBO therapy.
Vascular compromise can be caused by intrinsic disease, such as cardiovascular disease and peripheral vascular disease: atherosclerosis, thrombosis, and embolic disease on the arterial side and peripheral venous disease (stasis and thrombosis) on the venous side.
Testing via arteriography, venography, and ultrasound are useful in determining any vascular compromise and its extent.
- Vascular compromise can be due to injury: Lacerations and other trauma, including crushing, frostbite, burns, infection, and surgical complications.
- Testing for blood supply both at the site of injury and distal to it is necessary to assess the healing potential.
Anemia is another type of vascular compromise in that reduced numbers of red blood cells deliver less oxygen, the end result of which can be no different from a person without anemia having blood vessel compromise.
- Tests for anemia: Complete Blood Count (CBC)–as well as for causes of anemia (Vitamin B12 and folic acid deficiency testing) are useful to indicate patients that need this addressed in conjunction with hyperbaric oxygen therapy.
- Tests for coagulation: Coagulation defects and their causes (e.g., vitamin K) can be evaluated since they can affect healing and jeopardize the positive effects of hyperbaric therapy.
How Is Hyperbaric Oxygen Therapy Managed?
Most hyperbaric oxygen chambers are designed for single occupancy, although there are facilities with chambers that can accommodate more than one person. They are pressurized such that the chambers have an increased atmospheric pressure of 2.5-3 atmospheres (normal = 1 atmosphere).
100% oxygen delivered in a hyperbaric oxygen chamber will, in effect, deliver “250-300%” O2, depending on the atmospheric pressure.
Each therapy session can last from 45-300 minutes and is repeated according to individualized protocols, depending on the indication. For example, some acute conditions require only a few visits, whereas chronic medical conditions may require up to 30 sessions or more.
Uses for hyperbaric oxygen therapy include emergency treatment for carbon monoxide poisoning, decompression sickness, and arterial gas embolism. Uses related to chronic conditions include
- Necrotizing wounds, including gas gangrene (Clostridium myonecrosis)
- Osteomyelitis (bone infection)
- Radiation damage to bone and soft tissue from cancer treatment
- Poorly vascularized skin grafts, flaps, and wound care
- Healing in burn management
Prevention of Surgical Vascular Complications
Hyperbaric oxygen therapy can be used pre-operatively to reduce the risk of surgical vascular compromise and post-operatively to enhance healing. Surgeries that have an increased risk of jeopardizing blood supply, such as debridement for osteonecrosis, may benefit from both the pre-operative and post-operative application of HBO therapy.
Prevention of HBO Therapy Complications
Prevention of ill effects from hyperbaric oxygen (HBO) therapy are typically related to oxygen toxicity resulting from too much oxygen (100% delivered at multiple atmospheres), too long a duration of each therapy session, or summation of effects from too many sessions.
Avoidance of pulmonary or neurologic toxicity is based on serial observations of patients as they progress along their therapeutic protocols. Because of the hyperbaric effect on the lens, patients should have a thorough eye exam prior to HBO therapy. Those with benign or malignant tumors should consider the growth enhancement potential that HBO therapy could render. For example, women with small fibroids of the uterus may experience a growth spurt in them that may exacerbate their size with HBO therapy, impacting fertility.
Prevention of Claustrophobia
Patients who are claustrophobic should not use hyperbaric oxygen chambers unless they agree to some mild sedation.