Background: In prior military randomized trials, participants with persistent symptoms after mild traumatic brain injury (TBI) reported improvement regardless of receiving hyperbaric oxygen (HBO₂) or sham intervention. This study’s objectives were to identify outcomes for future efficacy trials and describe changes by intervention.

Methods: This Phase II, randomized, double-blind, sham-controlled trial enrolled military personnel with mild TBI and persistent post-concussive symptoms. Participants were randomized to receive 40 HBO₂ (1.5 atmospheres absolute (ATA), ⟩99% oxygen, 60 minutes) or sham chamber sessions (1.2 ATA, room air, 60 minutes) over 12 weeks. Participants and evaluators were blinded to allocation. Outcomes assessed at baseline, 13 weeks and six months included symptoms, quality of life, neuropsychological, neurological, electroencephalography, sleep, auditory, vestibular, autonomic, visual, neuroimaging, and laboratory testing. Participants completed 12-month questionnaires. Intention-to-treat results are reported.

Results: From 9/11/2012 to 5/19/2014, 71 randomized participants received HBO₂ (n=36) or sham (n=35). At baseline, 35 participants (49%) met post-traumatic stress disorder (PTSD) criteria. By the Neurobehavioral Symptom Inventory, the HBO₂ group had improved 13-week scores (mean change -3.6 points, P=0.03) compared to sham (+3.9 points). In participants with PTSD, change with HBO₂ was more pronounced (-8.6 vs. +4.8 points with sham, P=0.02). PTSD symptoms also improved in the HBO₂ group, and more so in the subgroup with PTSD. Improvements regressed at six and 12 months. Hyperbaric oxygen improved some cognitive processing speed and sleep measures. Participants with PTSD receiving HBO₂ had improved functional balance and reduced vestibular complaints at 13 weeks.

Conclusions: By 13 weeks, HBO₂ improved post-concussive and PTSD symptoms, cognitive processing speed, sleep quality, and balance function, most dramatically in those with PTSD. Changes did not persist beyond six months. Several outcomes appeared sensitive to change; additional studies are warranted.

Keywords: BIMA study; NCT01611194; www.ClinicalTrials.gov.

Weaver LK, Wilson SH, Lindblad AS, Churchill S, Deru K, Price RC, Williams CS, Orrison WW, Walker JM, Meehan A, Mirow S. Hyperbaric oxygen for post-concussive symptoms in United States military service members: a randomized clinical trial. Undersea Hyperb Med. 2018 Mar-Apr;45(2):129-156. PMID: 29734566.