Despite anecdotal reports that hyperbaric oxygen chambers can be used to treat concussions, strong evidence is mounting that they don't.
The latest strike against the increasingly popular therapy is a study of U.S. service members with persistent concussive symptoms, including headaches, balance problems, fatigue, forgetfulness, irritability and anxiety.
Those who spent 40 sessions in a pressurized chamber breathing pure oxygen saw no more improvement than a control group that completed the same number of sessions in a lower-pressure chamber breathing normal air.
Both groups, however, fared significantly better than a third group that received only standard care. The gains most likely resulted from some combination of a placebo effect and the daily ritual of interacting with the study staff, scientists said.
"This was a healing environment," two experts not involved in the research wrote in an editorial that accompanied the study, published Monday in JAMA Internal Medicine. "Hyperbaric oxygen treatment does not work, but the ritual of intervention does."
Hyperbaric oxygen chambers, which increase blood delivery to body tissues, are approved by the U.S. Food and Drug Administration for 14 uses, including decompression illness in scuba divers, carbon monoxide poisoning and certain soft-tissue infections.
They are also advertised for a variety of off-label uses not covered by insurance, including treatment of autism, stroke and migraines. Each session typically costs $200 to $400.
Last year the FDA warned consumers that unproven claims about hyperbaric oxygen therapy abound on the Internet.
Its use to treat concussions was championed by Dr. Paul Harch, a hyperbaric medicine specialist at Louisiana State University. He reported that his patients were seeing improvements after getting treatments that tripled the amount of oxygen delivered to the brain.
The Department of Defense took notice. In most cases, concussion systems disappear within a few weeks. But for up to 15 percent of service members, symptoms are still present after three to 12 months.
The new study in JAMA Internal Medicine involved 72 service members who had served in Iraq or Afghanistan and suffered at least one concussion during their deployments. They were being treated at military hospitals in Colorado, North Carolina, California and Georgia for symptoms that persisted for at least four months.
The 72 patients were randomly assigned to receive the oxygen therapy, the sham treatment or standard care for 10 weeks. Afterward, both groups that spent time in hyperbaric chambers — one breathing pure oxygen, the other regular air — averaged a 30 percent reduction in their concussion-related symptoms, based on their responses to a standardized questionnaire.
Those who also suffered from things like post-traumatic stress disorder, depression, sleep problems and anxiety — all of which were common among the study subjects — saw those conditions improve as well. In some ways, that was not surprising, because their symptoms often overlap with those of concussions.
But the gains came in sharp contrast to the lack of any meaningful progress in the group that never entered a chamber.
Dr. Scott Miller, the lead author of the study and an internist at the Uniformed Service University of the Health Sciences, said his team is continuing to follow the service members. If their improvements persist, researchers will be left to figure out which elements of the treatment ritual — as opposed to the treatment itself — are responsible.
"Shams are not benign," he said. "We're continuing to try to find what works."
The study is the most rigorous clinical trial to date testing hyperbaric oxygen therapy in concussion patients. It comes on the heels of two other randomized controlled trials conducted by the military; neither reported a benefit unique to the therapy.
A fourth, more extensive controlled trial is underway and on track to be completed next year.
"We're not planning any further studies beyond what's already ongoing," Miller said.
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