Intervention: Oxygen
Trial phase: Phase 2
ATC code: V03AN01
SMILES: O=O
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 24
Group description: Routine PCS care supplemented with hyperbaric oxygen (HBO2) at the dose of 1.5 ATA for 60 minutes administered over 40 sessions given daily Monday through Friday

hyperbaric oxygen: The chamber will be compressed with air to 1.5 atm abs. Once the chamber is compressed to 1.5 atm abs, the subjects will don a hood and breathe 100% oxygen. Hoods will be supplied with oxygen with flows of at least 30 liters per minute and overboard dumping of excess gas. Each subject will complete 40 sessions.

The duration of the hyperbaric oxygen exposures will be 60 minutes (±2 minutes), timed from when the chamber hatch or door closes, and ending when the chamber hatch or door opens ("door-to-door" time equals 60 minutes). The total intervention exposure time is 50 minutes (±2 minutes). The interval to compress to the intervention pressure (1.5 atm abs) and will be 5 minutes (±1 minute). The interval to decompress from the study pressure will be 5 minutes (±1 minute).
Eligibility criteria:
Inclusion Criteria:

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

Brain injury that occurred more than 4 months prior to enrollment, with the most recent injury occurring no earlier than October 7, 2001.
Most recent traumatic brain injury occurred while serving on active duty, and while deployed to the United States (US) Central Command (USCENTCOM).
Most recent traumatic brain injury was caused by blast exposure or blunt trauma.
Most recent traumatic brain injury resulted in at least one of the following: 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).

Volunteers must also meet all the following criteria:

18-65 years old at the time of study enrollment.
A TRICARE beneficiary at the time of consent and during study participation.
Has current complaints of brain injury symptoms such as headache, dizziness, or cognitive or affective problems that score at least 3 post-concussive symptoms as assessed by the Ohio State University (OSU) Traumatic Brain Injury (TBI) Identification (ID) Method interview
Has received current local care pharmacologic and non-pharmacologic interventions for TBI and any concomitant posttraumatic stress disorder (PTSD) with no significant change in therapy for at least 1 month
Willing and committed to comply with the research protocol and complete all outcome measures.
Able to self-consent.
Able to speak and read English, as primary language.
Able to participate in all outcome measures.
Able to equalize middle ear pressure.

Exclusion Criteria:

History of brain injury of moderate or severe degree: duration of loss of consciousness at the time of injury greater than 30 minutes, or duration of post-traumatic amnesia greater than 24 hours, or brain injury of a penetrating etiology.
History of brain injury not of traumatic etiology, such as stroke or drug-induced coma.
Prior treatment with HBO2.
Hyperbaric chamber inside attendant, professional (paid)underwater diver (commercial, operational/ military, instructor), or technical diver.
Pregnancy, women who plan to become pregnant during the study period, women who do not agree to practice an acceptable form of birth control during the study period, or women who are breastfeeding;
Those who are unable to participate fully in outcome assessments (Blind in one or both eyes; Deaf in one or both ears; or Ambulation with assistive devices
Pre-existing diagnosis of a psychotic disorder(s): schizophrenia, dissociative disorder, and bipolar disease.
Verifiable degenerative mental disease (e.g., Alzheimer's disease, multiple sclerosis, senile dementia).
Epilepsy or seizure disorder requiring anticonvulsants.
Active malignancy, prior malignancy (except basal cell carcinoma) within the last 5 years.
Presence of chronic debilitating disease (e.g., end-stage renal disease, end-stage liver disease, all types of diabetes with or without sequelae).
Documented clinically significant uncorrected anemia
Documented sickle cell disease.
History of therapeutic ionizing radiation to the head.
Verifiable diagnosis of learning disability.
Positive urine test for an illicit substance(s).
Any condition or use of prescribed medication (lithium, cisplatin, doxorubicin, or bleomycin) in which receipt of HBO2 would impact the safety of the individual.
Anticipated administrative separation, prolonged temporary assigned duty (TAD/TDY) or deployment within 3 months after randomization
Claustrophobia (unwilling or unable to enter hyperbaric chamber).
Inability to protect airway or requires frequent suctioning; presence of tracheostomy
Heart failure with ejection fraction < 50% (due to increased risk for precipitating acute lung edema during exposure to HBO2).
Emphysema, chronic bronchitis, or bullous lung disease (due to risk for pulmonary barotrauma during hyperbaric decompression).
Diabetes (relative contraindication related to risk of hypoglycemia).
Presence of implanted device (e.g., cardiac defibrillator, intrathecal drug delivery device, cochlear implant) that poses increased risk to subject during hyperbaric exposure.