Hyperbaric Oxygen Therapy (HBO)
Hyperbaric Oxygen Therapy (HBOT) is a medical treatment in which the patient is entirely enclosed in a pressure chamber breathing 100% pure oxygen (O2) at greater than one atmosphere pressure.
Air contains nearly 21% oxygen, and approximately 78% nitrogen. In hyperbaric oxygen therapy (HBOT), the oxygen percentage breathed by the patient is nearly or actually 100%, almost five times more than in air.
The pressure of the oxygen breathed by the patient in HBOT is usually
more than 1.5 times (and can be as much as 3 times) greater than atmospheric pressure.
HBOT can deliver nearly 15 times as much oxygen as there is in air at normal pressure.
- Hyperoxygenation: HBOT physically dissolves extra oxygen into the blood plasma, which is then delivered to the tissues. Breathing pure oxygen at two to three times normal pressure delivers 10-15 times as much physically dissolved oxygen to tissues. This can increase the tissue oxygen in compromised tissues to greater-than-normal values. Hyperoxygenation has been demonstrated to induce formation of new capillaries in ischemic or poorly perfused wounds. Therefore, it is useful in the treatment of ischemic based compromised wounds, flaps and grafts. It is also helpful in some infections by allowing white cell (leukocytic) activity to resume function.
- Mechanical Effect of Increased Pressure: Any gas in the body will decrease in volume as the pressure on it increases. With a threefold increase in pressure, a bubble trapped in the body is reduced by two-thirds. Thus, reduction in gas volume resolves air embolism and decompression illness when the diagnosis to treatment is done in a timely manner.
- Vasoconstriction: High-pressure oxygen causes constriction of the blood vessels in normal tissues without creating hypoxia. It does not cause constriction in previously oxygen-deprived tissues. The vasoconstriction decreases edema which is helpful in the treatment of burns, crush injuries, compartment syndromes and other acute traumatic ischemias. Even though the blood flow that contributes to edema is reduced, oxygen delivery to the tissues is maintained through the hyperoxygenation effect.
- Antimicrobial Activity: HBOT inhibits alpha toxin production as seen in anaerobic infections such as clostridium perfringens (gas gangrene). The most common cause of gas gangrene is clostridium perfringens; however, there are several gas producing organisms (aerobic and anaerobic) that require surgical debridement initially. It also enhances the white cell killing activity which provides an excellent adjuvant to I.V. antibiotic and local wound care.
- Mass Action of Gases: The flooding of the body with any one gas tends to "wash out" others. This action occurs more rapidly under pressure than under ordinary conditions, and makes HBOT an indicated treatment for decompression sickness.
- Reduction of Reperfusion Injury: Following an ischemic interval, indirect injury occurs, which is mediated by the inappropriate activation of leukocytes. HBOT prevents such activation. Adherence of white blood cells to capillary walls is markedly reduced, thus mitigating the "no reflow" phenomenon. This is why HBOT therapy is indicated in carbon monoxide poisoning and is considered the treatment of choice.
- Air or Gas Embolism
- Carbon Monoxide Poisoning Carbon Monoxide Poisoning Complicated by Cyanide Poisoning
- Clostridal Myositis and Myonecrosis (Gas Gangrene)
- Crush Injury, Compartment Syndrome, and other Acute Traumatic Ischemias
- Decompression Sickness
- Enhancement of Healing in Selected Problem Wounds
- Exceptional Blood Loss (Anemia)
- Intracranial Abscess
- Necrotizing Soft Tissue Infections
- Refractory Osteomyelitis
- Delayed Radiation Injury (Soft Tissue and Bony Necrosis)
- Compromised Skin Grafts & Flaps
- Thermal Burns
By definition, hyperbaric oxygen therapy is administered to a patient in a pressurized chamber. The hyperbaric chamber is a steel, aluminum or clear plastic room in which air can be compressed to a pressure that is greater than sea level. There are basically two types of chambers, monoplace and multiplace.
- Monoplace Chambers: A monoplace chamber is a system that accommodates one patient at a time. The patient lies down on a stretcher which slides into the chamber. Typically the chamber is pressurized with 100% oxygen. The patient receives 100% oxygen by breathing the oxygen inside of the chamber. A mask or a hood is not needed. Monoplace chambers have the capability to be pressurized to 3 ATA. Other than decompression sickness and gas embolism, the UHMS protocols for hyperbaric therapy do not require greater than 3 ATA of pressure for treatment. Critically ill patients requiring extensive life support equipment can be treated in the Sechrist monoplace. (Other monoplace manufacturers do not offer all the life support capabilities). The vast majority of hyperbaric patients are treated in a monoplace chamber.
- Multiplace Chambers: A multiplace chamber is a system that can accommodate two or more occupants. Patients can either walk or be wheeled (sitting or lying down) into a multiplace chamber, depending on the size. Typically, an attendant is inside with the patients. The chambers are pressurized with compressed air through a dedicated supply system. 100% oxygen is delivered to the patient via a mask or a hood assembly. Multiplace chambers have the capability to be pressurized to 6 ATA. Higher pressures may be desired in treatment of decompression sickness and air embolism cases.
The most common side-effects are not serious, those include:
- Ear “popping”
- Temporary myopia
- Lung problems in rare cases, the lungs become irritated by the oxygen, and the patient develops a dry cough that is resolved once the treatment is stopped.
In extremely small number of cases, some patients have developed non-life threatening issues. Overall, HBOT is a safe procedure.