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Hyperbaric medicine, also known as hyperbaric oxygen therapy (HBOT), is the medical use of oxygen at a level higher than atmospheric pressure. The equipment required consists of a pressure chamber, which may be of rigid or flexible construction, and a means of delivering 100% oxygen. Operation is performed to a predetermined schedule by trained personnel who monitor the patient and may adjust the schedule as required. HBOT found early use in the treatment of decompression sickness, and has also shown great effectiveness in treating conditions such as gas gangrene and carbon monoxide poisoning. More recent research has examined the possibility that it may also have value for other conditions such as cerebral palsy and multiple sclerosis, but no significant evidence has been found.In the United States the Undersea and Hyperbaric Medical Society, known as UHMS, lists approvals for reimbursement for certain diagnoses in hospitals and clinics. The following indications are approved (for reimbursement) uses of hyperbaric oxygen therapy as defined by the UHMS Hyperbaric Oxygen Therapy Committee:
Air or gas embolism;
Carbon monoxide poisoning; Carbon monoxide poisoning complicated by cyanide poisoning;
Central retinal artery occlusion
Clostridal myositis and myonecrosis (gas gangrene);
Crush injury, compartment syndrome, and other acute traumatic ischemias;
Enhancement of healing in selected problem wounds; Diabetically derived illness, such as diabetic foot, diabetic retinopathy, diabetic nephropathy;
Exceptional blood loss (anemia);
Idiopathic sudden sensorineural hearing loss;
Necrotizing soft tissue infections (necrotizing fasciitis);
Delayed radiation injury (soft tissue and bony necrosis);
Skin grafts and flaps (compromised);
Evidence is insufficient as of 2013 to support its use in autism, cancer, diabetes, HIV/AIDS, Alzheimer’s disease, asthma, Bell’s palsy, cerebral palsy, depression, heart disease, migraines, multiple sclerosis, Parkinson’s disease, spinal cord injury, sports injuries, or stroke. Despite the lack of evidence, in 2015, the number people utilizing this therapy has continued to rise.
Recent studies have indicated that HBO therapy is recommended and warranted in those patients with idiopathic sudden deafness, acoustic trauma or noise-induced hearing loss within 3 months after onset of disorder.
HBOT in diabetic foot ulcers increased the rate of early ulcer healing but does not appear to provide any benefit in wound healing at long term follow-up. In particular, there was no difference in major amputation rate. For venous, arterial and pressure ulcers, no evidence was apparent that HBOT provides an improvement over standard treatment.
There are signs that HBOT might improve outcome in late radiation tissue injury affecting bone and soft tissues of the head and neck. In general patients with radiation injuries in the head, neck or bowel showed an improvement in quality of life after HBO therapy. On the other hand, no such effect was found in neurological tissues. The use of HBOT may be justified to selected patients and tissues, but further research is required to establish the best patient selection and timing of any HBO therapy.
There is tentative evidence for HBOT in traumatic brain injury. As of 2012 there is insufficient evidence to support its general use in TBI. In stroke HBOT does not show benefit. HBOT in multiple sclerosis has not shown benefit and routine use is not recommended.
A 2007 review of HBOT in cerebral palsy found no difference compared to the control group. Neuropsychological tests also showed no difference between HBOT and room air and based on caregiver report, those who received room air had significantly better mobility and social functioning. Children receiving HBOT were reported to experience seizures and the need for tympanostomy tubes to equalize ear pressure, though the incidence was not clear.
In alternative medicine, hyperbaric medicine has been promoted as a treatment for cancer, but there is no evidence it is effective for this purpose.
The toxicology of the treatment has recently been reviewed by Ustundag et al. and its risk management is discussed by Christian R. Mortensen, in light of the fact that most hyperbaric facilities are managed by departments of anaesthesiology and some of their patients are critically ill.
The only absolute contraindication to hyperbaric oxygen therapy is untreated tension pneumothorax. The reason is concern that it can progress to tension pneumothorax, especially during the decompression phase of therapy. The COPD patient with a large bleb represents a relative contraindication for similar reasons. Also, the treatment may raise the issue of Occupational health and safety (OHS), which has been encountered by the therapist.
Patients should not undergo HBO therapy if they are taking or have recently taken the following drugs:
Doxorubicin (Adriamycin) – A chemotherapeutic drug. This drug has been shown to potentiate cytotoxicity during HBO therapy.
Cisplatin – Also a chemotherapeutic drug.
Disulfiram (Antabuse) – Used in the treatment of alcoholism.
Mafenide acetate (Sulfamylon) – Suppresses bacterial infections in burn wounds
The following are relative contraindications — meaning that special consideration must be made by specialist physicians before HBO treatments begin:
COPD with air trapping – can lead to pneumothorax during treatment.
Upper respiratory infections – These conditions can make it difficult for the patient to equalise their ears or sinuses, which can result in what is termed ear or sinus squeeze.
High fevers – In most cases the fever should be lowered before HBO treatment begins.
Emphysema with CO2 retention – This condition can lead to pneumothorax during HBO treatment.
History of thoracic (chest) surgery – This is rarely a problem and usually not considered a contraindication. However, there is concern that air may be trapped in lesions that were created by surgical scarring. These conditions need to be evaluated prior to considering HBO therapy.
Malignant disease: Cancers thrive in blood-rich environments but may be suppressed by high oxygen levels. HBO treatment of individuals who have cancer presents a problem, since HBO both increases blood flow via angiogenesis and also raises oxygen levels. Taking an anti-angiogenic supplement may provide a solution. A study by Feldemier, et al. and recent NIH funded study on Stem Cells by Thom, et al., indicate that HBO is actually beneficial in producing stem/progenitor cells and the malignant process is not accelerated.
Middle ear barotrauma is always a consideration in treating both children and adults in a hyperbaric environment because of the necessity to equalise pressure in the ears.
Pregnancy is not a relative contraindication to hyperbaric oxygen treatments, although it may be for SCUBA diving. In cases where a pregnant woman has carbon monoxide poisoning there is evidence that lower pressure (2.0 ATA) HBOT treatments are not harmful to the fetus, and that the risk involved is outweighed by the greater risk of the untreated effects of CO on the fetus (neurologic abnormalities or death.) In pregnant patients, HBO therapy has been shown to be safe for the fetus when given at appropriate levels and “doses” (durations). In fact, pregnancy lowers the threshold for HBO treatment of carbon monoxide-exposed pregnant patients. This is due to the high affinity of fetal hemoglobin for CO.
Several therapeutic principles are made use of in HBO
The increased overall pressure is of therapeutic value when HBOT is used in the treatment of decompression sickness and air embolism as it provides a physical means of reducing the volume of inert gas bubbles within the body.
For many other conditions, the therapeutic principle of HBOT lies in its ability to drastically increase partial pressure of oxygen in the tissues of the body. The oxygen partial pressures achievable using HBOT are much higher than those achievable while breathing pure oxygen at normobaric conditions (i.e. at normal atmospheric pressure);
A related effect is the increased oxygen transport capacity of the blood. Under normal atmospheric pressure, oxygen transport is limited by the oxygen binding capacity of hemoglobin in red blood cells and very little oxygen is transported by blood plasma. Because the hemoglobin of the red blood cells is almost saturated with oxygen under atmospheric pressure, this route of transport cannot be exploited any further. Oxygen transport by plasma, however is significantly increased using HBOT as the stimulus.
Recent evidence notes that exposure to hyperbaric oxygen (HBOT) mobilizes stem/progenitor cells from the bone marrow by a nitric oxide (·NO) -dependent mechanism. This mechanism may account for the patient cases that suggest recovery of damaged organs and tissues with HBOT.
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