Hyperbaric oxygen therapy
Hyperbaric oxygen therapy is defined as administration of 100% oxygen to a patient placed inside a chamber pressurised to greater than 1 atmosphere at sea level. Local application of pressurized oxygen to a part of the body without completely enclosing the patient is not hyper baric oxygen therapy.
In 1662 a British clergyman Henshaw first built a sealed chamber where compressed oxygen was given as a cure to various ailments. He also used the term Domicilium to describe the chamber. Following discovery of oxygen by Joseph Priestely it has been used to treat various chronic conditions at high pressures.
It was Dr I. Boerema in 1956 who demonstrated the value of oxygen under high pressure in management of certain difficult cardiovascular conditions.
Indications of Hyperbaric oxygen therapy:
1. Arterial air or gas embolism
2. Acute blood loss anaemia
3. Carbon monoxide poisoning, cyanide poisoning, and smoke inhalation
4. Compromised skin grafts and flaps
5. Crush injury
6. Decompression sickness
7. To facilitate enhanced wound healing
8. Gas gangrene
9. Necrotising soft tissue infections
10. Radiation necrosis: Osteoradionecrosis, soft tissue radionecrosis, caries in radiated bones
11. Refractory osteomyelitis
12. Refractory mycosis
13. Thermal burns
Mechanism of action:
1. Hyperoxygenation - is achieved by first completely saturating the hemoglobin and then by increasing the amount of oxygen dissolved in the plasma. This increases the distance of oxygen diffuses away from the capillaries. This is three times higher than under normal conditions.
2. Vasoconstriction - Vasoconstriction caused by hyperbaric oxygen therapy does not reduce oxygenation, on the contrary it has a benefical effect of reducing edema in skin grafts and flaps.
3. Anitmicrobial activity - Hyperbaric oxygen therapy is bactericidial to obligate anaerobes. It also increases the ability of polymorphs to kill bacteria. It is also known to inhibit and inactivate the toxins released by clostridium welchi, thereby preventing gas gangrene.
4. Pressure effects - Hyperbaric oxygen is used to reduce the size of gas bubble. Because of this feature it is the treatment of choice in decompression sickness.
6. Fibroblastic proliferation
7. Improved functioning of osteoblasts and osteoclasts
8. Increased red cell deformability
Complications of hyperbaric oxygen therapy:
1. Middle ear barotrauma - This can occur if the patient is unable to equalize the middle ear pressure. This complication can be best avoided by the use of systemic and topical nasal decongestants before proceeding with hyperbaric oxygen therapy. If this condition occurs then myringotomy should be resorted to without hesitation.
2. Myopia - This is temporary and reverses back to normal after cessation of treatment.
3. Pneumothorax - can occur if decompression occur too rapidly or if the patient holds the breath during decompression.
4. Oxygen induced seizures - This complication is very rare. These patients should be given vitamin E before treatment to protect against superoxide radicals. Oxygen induced seizures can be stopped by allowing the patient to breath normal air. Oxygen induced seizures are not known to cause permanent neurological sequlae.
How to administer hyperbaric oxygen?
Hyperbaric oxygen is administered by placing the patient inside oxygen chambers. Two types of chambers are commonly used for hyperbaric oxygen therapy. 1. Monoplace and 2. Multiplace chambers. In both these chambers facilities are provided for monitoring the various vital body parameters like heart rate, blood pressure and blood oxygen levels etc. Facilities are provided for intravenous administration of drugs and fluids.
Monoplace chamber: Here 100% pressurised oxygen is utilized. Patient alone is placed in this type of chamber. There is no space for attendants. The patient is placed alone inside this chamber. This chamber is hence not useful in critically ill patients.
Multiplace chamber: These chambers are pressurised with air. Patients inside this chamber are administered 100% oxygen via a face mask or hood. These chambers allow one or more attendants inside them. This feature is advantageous in treating seriously ill patients.
Regardless of the type of chamber used the following factors must be considered:
1. The amount of pressure used.
2. Duration of the treatment.
3. How often the treatment is repeated.
To avoid oxygen toxicity the treatment duration should not exceed 120 minutes. The safe range being 90 - 120 minutes. The pressure used is about 2 atmospheres. When a patient's condition require multiple hyperbaric oxygen treatments per day, a minimum duration of 6 hours between them is a must.
Indications of hyperbaric oxygen therapy:
1. Radiation induced soft tissue necrosis: Hyperbaric oxygen therapy promotes neovascularisation. Hypoxia is corrected and wound heals faster.
2. Osteoradionecrosis: Hyperoxygenation and neovascularisation helps in treating this difficult condition. Hyperbaric oxygen treatment is an effective adjuvant to antibiotics in managing this condition.
3. Prevention of mandibular osteoradionecrosis
4. In treating necrotising soft tissue infections
5. In management of malignant otitis externa
6. Can be used in management of fungal infections of head and neck. This has a proven value as an adjunct to the regular antifungal agents.
7. Managment of acute blood loss anaemia
8. Can be used to salvage compromised skin grafts and flaps
9. Can be used as an adjunct in the management of patients with burns
10. Can be used to manage air or gas embolism
Contraindications of hyperbaric oxygen therapy:
2. Pulmonary damage
1. Pulmonary bulla
2. Seizure disorder
3. Patients on high dose of steroids
4. Chronic obstructive pulmonary disorders
5. Recent myocardial infarction
6. Patients with claustrophobia