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Author: Juhee Roh, Medical Student, University of Auckland, Auckland, New Zealand. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Hamilton, New Zealand. Copy edited by Gus Mitchell. July 2019.
Hyperbaric oxygen therapy is a treatment in which a patient breathes pure oxygen while subject to increased levels of atmospheric pressure. It is a primary or adjunctive treatment for carbon monoxide poisoning, severe decompression sickness, arterial gas embolism, and chronic wounds .
There are over 500 hyperbaric facilities in the United States, but hyperbaric oxygen is less widely used elsewhere .
Hyperbaric oxygen therapy is primarily used to treat patients with:
Carbon monoxide [CO] poisoning can occur on inhaling combustion fumes, especially in an enclosed space. Occupations at risk include firefighters, miners, and people exposed to a charcoal or gas fire indoors with inadequate ventilation [4,5]. Carbon monoxide poisoning is also induced by cyanide.
Decompression sickness occurs most commonly in scuba or deep-sea divers breathing compressed air. It also occurs at high-altitude or during deep pressurised air travel .
Arterial gas embolism also occurs during diving and after unexpected rapid depressurisation of an aeroplane or spacecraft above 5500 metres altitude . Air can also be directly introduced into the circulation during central venous catheter placement, cardiac, neurological, and otolaryngological surgery . People who have a patent foramen ovale are at an increased risk of arterial gas embolism .
Poor wound healing can be due to local, regional, systemic, or miscellaneous causes. It can occur in those with tissue ischaemia, active bacterial skin infection, arterial and venous insufficiency, diabetes mellitus, exposure to radiation, smoking, and the use of vasoconstrictive drugs .
Hyperbaric oxygen is sometimes used to treat a diverse range of medical conditions, including:
Hyperbaric oxygen can improve healing after acute traumatic crush injury and compartment syndrome resulting in fewer skin flaps, grafts, and amputations [12,13]. In contrast, there is insufficient evidence to support the use of hyperbaric oxygen for burns [14,15].
The use of hyperbaric oxygen for soft tissue radionecrosis and osteoradionecrosis is controversial [16–20]. Current guidelines for prevention and treatment recommend 20 to 30 preoperative 90-minute sessions of hyperbaric oxygen at 2.4 atm (atmospheres) followed by 10 postoperative sessions .
Hyperbaric oxygen is used as an adjunctive treatment for aggressive soft tissue infections such as clostridial myonecrosis (gas gangrene), necrotising fasciitis, and Fournier gangrene [21–27]. It should be commenced early, with two to three daily 90-minute sessions at 3 atm . It is unclear whether hyperbaric oxygen therapy is useful for cutaneous soft-tissue and rhinocerebral mucormycosis (zygomycosis), actinomycotic brain abscesses, or refractory osteomyelitis .
Hyperbaric oxygen is used as an adjunctive therapy to treat non-healing ulcers, skin grafts, and to promote wound healing, although there is limited evidence to support its routine use [28–30]. Patients who require skin grafting or reconstructive flaps in areas with compromised blood flow, previous radiation therapy, or in sites of previous graft failure may benefit from prophylactic treatment.
Many other diseases have been treated with hyperbaric oxygen without evidence to support the treatment. Further research is required to confirm any benefits and justify its substantial costs and potential risks [1,31].
Hyperbaric oxygen therapy is usually performed as an outpatient procedure and does not require hospitalisation. Details depend on the hyperbaric oxygen facility and the indication for treatment.
Hyperbaric oxygen therapy involves breathing 100% pure oxygen in either a monoplace chamber (treats one patient at a time) or a multiplace chamber (treats two or more patients at once).
Pressures of 2.5 to 3.0 times normal atmospheric air pressure are generally recommended for both types of chamber .
The monoplace chamber is designed for one person and is appropriate for treatment of a chronic medical condition in a stable patient . The patient lies on a table that slides into a clear plastic tube, similar to an MRI machine .
The multiplace chamber is designed for two or more people and allows close monitoring of a critically ill patient [1,31]. The large chamber resembles a hospital room and the patient may sit or lie down. Oxygen is received through a mask or through a transparent, lightweight hood [3,31].
The mechanism of action depends on the condition being treated.
Carbon monoxide [CO] has 200–250 times greater affinity to haemoglobin than oxygen, reducing the oxygen-carrying capacity of the blood . The normal half-life of carboxyhaemoglobin is four to six hours; hyperbaric oxygen therapy reduces its half-life to 15–30 minutes [33,34].
According to Boyle’s Law (the relationship between gas concentration, volume and pressure), the volume of nitrogen bubbles decreases by approximately two-thirds at 3.0 atm. Hyperbaric oxygen therapy thus reduces the size of nitrogen gas bubbles and replaces inert nitrogen with oxygen . The residual nitrogen is metabolised in the tissues.
Hyperbaric oxygen therapy achieves its therapeutic effect by increasing the oxygen delivered to injured tissue.
The concentration of oxygen dissolved in plasma at sea level is 0.3 mL/dL. Applying the principles of Henry’s Law, hyperbaric oxygen administered at 3.0 atm results in a dissolved plasma oxygen concentration of 6 mL/dL . The delivery of oxygen in high concentration to injured tissues can restore tissue function, stimulate healing, and resist infection .
In vitro studies have demonstrated that reactive oxygen and nitrogen species are the key mediators in acute and chronic injury, ischaemia, and inflammation [35–37].
An excessive concentration of oxygen (local hyperoxia) induces the following effects:
Untreated pneumothorax is an absolute contraindication to hyperbaric oxygen therapy . Relative contraindications include:
Side effects of hyperbaric oxygen therapy may include:
The most common complication of hyperbaric oxygen therapy is middle ear barotrauma (pressure-related trauma) with an incidence of approximately 2%; this may infrequently result in middle ear effusions and tympanic membrane rupture . Pressure-related middle ear injury can be prevented through autoinflation techniques and placement of tympanostomy tubes .
The second most common complication is sinus barotrauma, which is usually seen in patients with upper respiratory tract infections or allergic rhinitis . The risk can be minimised by nasal decongestants, steroids, or histamines prior to hyperbaric oxygen .
Rare complications may include:
Pure oxygen is a serious fire risk.
Potential fire hazards such as lighters, battery-powered devices, and petroleum-based hair and skincare products should be removed prior to the procedure .
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