mTBI Mechanisms of Action of HBO2 for Persistent Post-Concussive Symptoms

Inclusion Criteria

• On active duty (TRICARE beneficiary) at the time of consent and through the 6-month visit or a Veteran, as well as Active Duty military who become Veterans after enrollment.
• Men and women 18-65 years of age at the time of study enrollment.
• Able to equalize middle ear pressure in a test of chamber pressure and tolerate the chamber environment.
• Able to speak and read English, as primary language.
• Agrees to and appears able to participate in all outcome assessments.
• Agrees to provide blood samples for clinical lab tests.
• Demonstrates the ability to offer informed consent and signs the study informed consent document.
• Participants stationed or living outside the Colorado Springs/Denver, Colorado area must be willing and able to travel. A reliable companion may accompany the participant if travel supervision is required.
• Active duty participants must obtain a letter of support from a supervisor or commanding officer prior to the outcome assessments (and travel, if necessary) to the OAC.

Participants must have a history of at least one (minimum requirement) mild traumatic brain injury (mTBI) with persistent symptoms that meets all the following criteria:

• Brain injury that occurred more than 3 months prior to baseline screening at the local site, with the most recent injury occurring no more than 5 years prior to randomization.
• Most recent traumatic brain injury (TBI) occurred on active duty.
• TBI was caused by non-penetrating trauma or blast exposure.
• TBI resulted in at least one of the following at the time of injury: a period of loss of or a decreased level of consciousness (up to 30 minutes); a loss of memory for events immediately before or after the injury (up to 24 hours); or alteration in mental state at the time of the injury (becoming dazed or confused).
• Has current complaints of TBI symptoms such as headache, dizziness, or cognitive or affective problems that score at least 3 post-concussive symptoms as assessed by the OSU TBI-ID.
• Has received current standard of care pharmacologic and nonpharmacologic interventions for TBI and any concomitant post traumatic stress disorder (PTSD) with no significant change in psychoactive therapy for at least 1 month.
• Creatinine level that is less than or equal to the EACH laboratory's upper limit of normal. If the creatinine level exceeds the EACH laboratory's upper limit of normal, participants cannot have a CT scan due to risk of contrast dye-induced renal failure. Such participants may be randomized but must be approved by the Study Director.

Exclusion Criteria

• Prisoners.
• Pregnant Women.
• Minors.
• Individuals whose most recent TBI was sustained during illegal activity.
• Potential active duty participants stationed >1 hour outside the designated recruitment area of a participating local site will be excluded unless the command authorizes temporary relocation and appropriate relocation resources.
• Potential Veteran participants who live >1 hour outside the designated recruitment area of a participating local site, must be willing and able to travel to the local site to participate in all required local site visits without additional financial assistance than that which is described in the Veteran Payment Schedule (consent attachment C).
• Active duty individuals with anticipated prolonged TAD/TDY or deployment within 6 months of study enrollment will be excluded.
• Veterans with anticipated prolonged travel or relocation within 6 months of study enrollment will be excluded.

An individual with any of the following characteristics will be excluded from this study based on contraindications to hyperbaric pressurization and hyperbaric oxygenation or other study assessment measures:

• Women who are pregnant or who plan to become pregnant during the study period.
• Women who are breastfeeding.
• Women of childbearing potential who do not agree to practice an acceptable form of birth control during the study period.
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