Hyperbaric Oxygen No Better Than Sham After Concussion

Pauline Anderson

November 26, 2014

Although hyperbaric oxygen (HBO) treatment is well tolerated by patients with postconcussion syndrome, and improves their symptoms and quality of life, it does not work any better than a sham air compression treatment, results of a new pilot study suggest.

The improvements are likely attributable to a placebo effect or to the benefits of intensive daily routine involving social interactions.

The study was among a series of trials funded by the Department of Defense (DOD) that tested different doses of HBO to try to determine the validity of anecdotal reports of improvements resulting from this treatment approach.

The results are "definitely disappointing," R. Scott Miller, MD, assistant professor, medicine and preventive medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, told Medscape Medical News. "We were all hopeful that it would be proven to be effective."

Still, a larger confirmatory trial funded by DOD will proceed, he said.

"Trying to find interventions to help our veterans who are struggling with symptoms is a high priority," he said. "Given the fact that there was improvement in the study, although it doesn't appear to be specifically to HBO, and because the confirmatory study has slightly larger sample sizes and is attempting to look at some of the underlying pathophysiologic changes that might be the mechanism of action, we felt it was important to continue that trial."

Dr Miller reported that that trial is fully enrolled and is following individuals for a year after the intervention. The results are expected to be released in early 2016.

The current study results were published online November 17 in JAMA Internal Medicine.


The Hyperbaric Oxygen Therapy for Persistent Post-concussive Symptoms After Mild Traumatic Brain Injury (HOPPS) was a pilot study designed to define significant postconcussion symptom change scores and to determine an effect size of symptomatic improvements by HBO compared with a sham procedure when supplementing routine care. It was hoped that the results would inform sample sizes for potential pivotal trials.

For the study, researchers enrolled 72 participants, median age 31 years, 96% of whom men, and 94% of whom were enlisted in the military service, mostly the Army and Navy. All were experiencing persistent postconcussion symptoms. Two thirds (66%) met criteria for posttraumatic stress disorder (PTSD), 48% were taking daily pain medication, and 60% were receiving an antidepressant.

These patients were randomly assigned to one of three study groups: treatments with HBO (100% oxygen delivered at 1.5 atmospheres absolute [ATA]), a sham procedure (slightly pressurized room air at 1.2 ATA), or routine postconcussion care only. The other DOD studies tested 2.4 and 2.0 ATAs, said Dr Miller.

The length and amount of the HBO intervention (40 hour-long sessions within a 10-week period) was determined through expert consensus, said Dr Miller.

Although it is difficult to mask HBO, the researchers chose a sham that is indistinguishable from HBO pressurization. "It has been shown in a previous clinical trial to cause popping in the ears and a pressure sensation within the face and sinus area, and people could not tell the difference with that level of pressurization," said Dr Miller.

There have been anecdotal reports that HBO improves cognitive function, but the exact mechanism by which HBO might affect postconcussion symptoms is unknown. However, possibilities could include "spawning of angiogenesis" that may change blood supply or blood flow within the brain, said Dr Miller.

The primary outcome of the study was change in scores of the 16-item Rivermead Post-Concussion Symptoms Questionnaire (RPQ). Researchers deemed a 15% improvement as clinically relevant, which translates to a change in score of at least 2 points on the RPQ-3 subscale, which measures dizziness, headache, and nausea.

The study found that routine care showed no improvement during the 3-month observational period, with a mean RPQ-3 subscale change of 0.0 (95% confidence interval [CI], −1.0 to 1.0; P = .97) and mean total RPQ change score of 0.5 (95% CI, −4.8 to 5.8; P = .91).

The HBO group had a mean change score of 1.2 (95% CI, 0.0 - 2.4; P = .04) on the RPQ-3 subscale and 5.4 (95% CI, −0.5 to 11.3; P = .008) on the total RPQ.

However. the group receiving sham treatment also improved: mean change in RPQ-3 subscale score, 1.5 (95% CI, 0.1 to 2.9; P = .03), and on the total RPQ, mean change 7.0 (95% CI, 1.0 - 12.9; P = .02).

Although greater, there were no meaningful differences between the HBO and sham groups in the percentage who met the prespecified change of at least 2 points on the RPQ-3.

The sham group tended to do better in terms of improvements in PTSD symptoms and in outcomes of depression, generalized anxiety, pain, and sleep. Measures of quality of life, such as physical functioning, bodily pain, and social functioning, also favored the sham group.

Both the HBO and hyperbaric air sham sessions were well tolerated. There were no serious adverse events, although two participants withdrew from chamber sessions because of claustrophobia in one case and worsening of headaches in the other.

Because this and the other two dose-ranging studies "could not reproduce the benefit independent of the changes seen in the sham," researchers believe the findings are a result of a marked placebo response, said Dr Miller. The HBO procedure, note the authors, involved "an intense ritual experience consisting of 2 hours of daily social interactions with a dedicated team of nurses and hyperbaric technicians as well as other participants."

The researchers acknowledge that the sham was not completely inert and that there are some increases in nitrogen or oxygen in the blood from pressurized room air, "but not at a level that any of our experts felt would be physiologically important," said Dr Miller.

Broad Implications

Writing in an accompanying editorial, Charles W. Hoge, MD, senior scientist, Walter Reed Army Institute of Research, Silver Spring, Maryland, and Wayne B. Jonas, MD, from the Samueli Institute, Alexandria, Virginia, describe the study as exemplary, unique, and well-designed, and said it provides "compelling results with broad implications."

The editorialists argue that the persistent postconcussion condition is such an elusive target for treatment that effective interventions will likely not be identified until the condition is "reconceptualized."

In an interview with Medscape Medical News, Dr Hoge said he has long argued that a more holistic approach is needed to treat the "chronic multisystem concerns," including headache and cognitive and memory problems, as well as physical complaints such as gastrointestinal and cardiovascular symptoms, that plague a large percentage of veterans returning from war.

Such holistic models of care involve multidisciplinary teams that are centered on primary care but also involve specialists in, for instance, neuropsychology, neurology, and mental health.

Although veterans' symptoms are often labeled as postconcussion, there is probably "underlying dysregulation" in the endocrine and autonomic nervous systems that occur when someone is exposed to a trauma such as a blast-related event, said Dr Hoge.

This is the latest in several trials that have looked at whether hyperbaric oxygen is effective in veterans suffering postconcussion symptoms. "I think there's enough evidence to say that we need to consider other options," said Dr Hoge. "There is pretty adequate evidence now to suggest that we should be looking at other types of treatments."

The HOPPS trial was funded by the Defense Health Program and was managed by the US Army Medical Materiel Development Activity. The Naval Health Research Center and Army Contracting Command contracted support throughout this trial. Dr Miller, Dr Hoge, and Dr Jonas have disclosed no relevant financial relationships.

JAMA Intern Med. Published online November 17, 2014. Article abstract, Editorial extract


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