A diver who ascends too quickly to the surface can end up in the decompression chamber.
As long ago as 1662, a British clergyman and physician called Henshaw built the first hyperbaric chamber, a sealed room with a series of bellows and valves. He believed that using pressure could help in treating certain respiratory diseases.
Since the 1940s, hyperbaric oxygen treatment (HBOT) has been standard treatment for military divers in the United States.
Divers who surface too quickly are at risk of decompression sickness (DCS), sometimes called "the bends," or of an air gas embolism (AGE). Jointly, these are known as decompression illness (DCI), and they both relate to problems with air in the body. Consequences can be severe. HBOT is the primary treatment for both.
Treatment involves early administration of oxygen, and, if necessary, time spent in a decompression chamber. The diver must return to the pressure, or "depth," at which they were diving, followed by gradual decompression. The pressure reduces the volume of the bubbles.
DCI affects around 1,000 American divers each year, but the uses of HBOT go beyond the diving community.
HBOT has been shown to benefit people with infections, embolism, or air bubbles in the blood vessels, and some wounds that do not respond to other treatment.
To meet the growing demand, HBOT chambers have sprung up across a range of facilities, from hospital outpatient departments to spas. There are even chambers for home use. Some call it a "miracle cure."
While research suggests that some of these claims may be true, not all of the suggested uses are approved by the U.S. Food and Drug Administration (FDA). Concerns have been raised about the risks associated with "off-label" use of HBOT.
How does hyperbaric oxygen therapy work?
The Undersea and Hyperbaric Medical Society (UHMS) - an international organization set up in 1967 to encourage cooperation on diving and undersea medicine - defines HBOT as:
"An intervention in which an individual breathes near 100 percent oxygen intermittently while inside a hyperbaric chamber that is pressurized to greater than sea level pressure (1 atmosphere absolute, or ATA). For clinical purposes, the pressure must equal or exceed 1.4 ATA [atmosphere absolute] while breathing near 100 percent oxygen."
The body's tissues need oxygen to work. Additional oxygen can help damaged tissue to heal. Oxygen at high pressure can enhance tissue function and fight infection, under certain conditions.
At 1.4 ATA, the ambient pressure is three times higher than the air pressure we normally breathe. Breathing almost pure oxygen at this pressure can increase the concentration of oxygen available to the lungs by up to three times.
What are the benefits of HBOT?
Working with the UHMS, the FDA have approved 13 uses of HBOT. Evidence has shown that they are safe and effective. Insurance companies or Medicare will normally cover the cost of treatment.
The approved uses are:
HBOT is approved in the treatment of certain wounds that do not respond to conventional treatment.
- Decompression sickness, experienced by divers and pilots
- Acute traumatic ischemia - for example, crush injury
- Air or gas embolism
- Arterial insufficiencies
- Anemia due to severe blood loss
- Thermal burns
- Carbon monoxide poisoning
- Some brain and sinus infections
- Intracranial abscess
- Gas gangrene
- Necrotizing soft tissue infections
- Radiation injury - for example, as a result of cancer therapy
- Skin grafts.
Wounds and infections that have not responded to other treatment, such as bone infections and diabetic foot ulcers, have been shown to respond to HBOT. HBOT has been found to reduce the risk of amputation in people with diabetic foot ulcers.
How is HBOT delivered?
HBOT is normally provided in an outpatient setting. The number of visits will depend on the condition.
A large HBOT chamber can accommodate many people at one time.
According to the Mayo Clinic, a person with carbon monoxide poisoning may need three sessions, while a person with a non-healing diabetic wound may need 20-40 sessions. An acute condition, such as DCI, may need only one longer session.
A chamber can hold one or many people, and the patient will probably wear a mask or hood that delivers oxygen.
In a chamber for one person, the patient usually lies on a table that slides into a clear plastic tube.
Nowadays, HBOT chambers encourage patients to be comfortable. They can relax by listening to music or watching TV.
A session can last from 30 minutes to 2 hours, after which the chamber is slowly decompressed.
What has HBOT not been approved for?
The FDA have expressed concern that HBOT is being used to treat conditions for which its safety and effectiveness have not been confirmed.
"Patients may incorrectly believe that these devices have been proven safe and effective for uses not cleared by FDA, which may cause them to delay or forgo proven medical therapies. In doing so, they may experience a lack of improvement and/or worsening of their existing condition(s)."
Nayan Patel, senior lead reviewer and Intercenter Consult team leader at the FDA
Diseases and conditions that the FDA believe people may wrongly seek HBOT for include HIV and AIDS, Alzheimer's and Parkinson's diseases, asthma, Bell's palsy, cerebral palsy, depression, heart disease, hepatitis, migraine, multiple sclerosis, sports injury, stroke, brain injury, and spinal cord injury.
In 2013, responding to a number of complaints, the FDA insisted that certain conditions should not be treated with HBOT. The Alliance for Natural Health (ANH) called the announcement a "deceptive statement."
There are suggestions that HBOT could help people with PTSD, and veterans in particular.
Those who support the use of HBOT for a wider range of conditions point out that pressure and additional oxygen can benefit various bodily functions. They cite a number of studies supporting their claims.
There are calls for HBOT to be approved as an alternative therapy for autism, attention deficit hyperactivity disorder (ADHD), cerebral palsy, and post-traumatic stress disorder (PTSD). There is strong support in certain circles for its use in helping improve the quality of life of veterans.
It is believed that HBOT can help to heal brain injury by improving the way dormant neurons function and stimulating the growth of axons. A meta-analysis published in May 2016 suggests that HBOT can enhance a patient's score on the Glasgow Coma Scale, but no significant change was seen in the PTSD score.
Dr. Paul Harch, hyperbaric medicine, diving, and emergency medicine physician, and coauthor of the book The Oxygen Revolution calls for wider approval of the uses of HBOT, and especially for TBI and neurological disorders.
Dr. Harch told Medical News Today:
"It was found that diseases and disorders with similar disease processes responded similarly to HBOT. In Russia nearly 100 diagnoses are treated and nearly 70 in China. We have been much more restricted in the U.S. based on reimbursement considerations."
The UHMA note that "meticulous scrutiny" is needed before new applications of HBOT can be approved for use in treating a condition. Each case involves a stringent review of a wide range of research by an interdisciplinary team.
More research is needed before the requested new uses can be implemented, say the FDA and the UHMA.
What are the risks of HBOT?
High atmospheric pressure can damage the ear. Middle ear barotrauma affected 2 percent of 1,446 participants in one study. A higher incidence of Eustachian tube dysfunction, up to 45 percent, has been detected using sensitive testing equipment.
People with certain lung diseases or an airway obstruction may be at risk of pulmonary barotrauma and damage to the lungs as a result of air becoming trapped during decompression. The result could be a collapsed lung or an air embolism. Long-term treatment could compromise lung function.
Those with existing cardiovascular problems should be monitored for acute pulmonary edema or an embolism. Symptoms include joint pain and paralysis.
Overexposure to oxygen at high pressure can lead to oxygen poisoning. When a person uses oxygen, highly reactive byproducts are released. At high pressure, these build up, saturating tissues and possibly leading to convulsions and other adverse effects.
Dr. Harch told MNT that some people, for example, those with seizure disorders should be treated by "medical professionals who have knowledge, experience, and hopefully training in the field."
Dr. Paul G. Harch
HBOT is not recommended for people who have undergone recent ear surgery or trauma.
A growing trend brings growing concerns
In January 2015, the Wall Street Journal reported that growing numbers of people are seeking out HBOT as a solution to problems that conventional medicine seems unable to resolve. In 2010, 20,000 Medicare beneficiaries had FDA-approved treatments using HBOT, up 24 percent from 2008.
Johns Hopkins Medicine urge caution in the choice of treatment setting. HBOT should only be carried out in a hospital, they say, with trained medical staff.
If Medicare and insurance do not cover the treatment, it may be because it has not yet been approved as safe and effective.
The WSJ point out that since not all the claims for HBOT are conclusively supported by evidence, people who seek unapproved treatments from small clinics and spas may be wasting their money. It is important for people to understand that HBOT is not a "magic bullet."
Non-hospital use may include "soft" or "mild" chambers that cannot sustain the necessary pressure, or guarantee the purity of the oxygen. As a result, the patient may undergo many treatments without seeing any benefit.
If the power is disrupted, the chamber could deflate, leading to suffocation. These chambers are not considered appropriate by many hyperbaric practitioners.
Since pure oxygen is highly explosive and flammable, a number of explosions have been reported.
HBOT may yet turn out to be a miracle cure. But, as with all health choices, it pays to be cautious.