Hyperbaric Oxygen Therapy (HBO2) for Persistent Post-concussive Symptoms After Mild Traumatic Brain Injury (mTBI)

Brain injury due to trauma is very common; nonetheless, no pharmacological therapy is known to improve outcomes. Medications are used to treat symptoms, such as seizures and affective disorders, but are not intended to affect the fundamental problem. If HBO2, which is regularly available and relatively safe, improves outcome in brain-injured subjects by treating the underlying pathophysiology of post-concussive syndrome, this would represent a significant advance in treatment of brain injury. Hyperbaric oxygen (HBO2) has been proposed as a treatment for patients with TBI.

Hyperbaric oxygen is one of the first pharmacologic interventions being tested in this population of individuals with mild TBI and chronic post-concussive symptoms targeted to improve cognition, memory, and functional status. However, much is unknown about how to measure improvement in post-concussive symptoms after an intervention in the targeted active duty population. In preparation for a pivotal efficacy study, the objectives of this study are to characterize two candidate primary outcome tools in our intended study population, the RPQ and the NSI, in order to better estimate the sample size needed to answer the efficacy question.

Agency for Healthcare Research and Quality (AHRQ) conducted a comprehensive review of the literature, interviewed subject matter experts (SME), and conducted focus groups with SMEs to evaluate the evidence for HBO2 for patients with TBI. The AHRQ concluded that "Although they are cited frequently, the case series and time-series studies of HBO2 for TBI patients had serious flaws. There were no high-quality studies of the use of HBO2 to improve function and quality of life in patients with chronic, stable disabilities from TBI. The most important gap in the evidence is a lack of a good quality time-series study or controlled trial of the effects of HBO2 on cognition, memory, and functional status in patients with deficits due to mild chronic TBI." Similarly, the Department of Health and Human Services (DHHS) has not approved HBO2 therapy for the treatment of TBI as a covered condition, citing the lack of supporting evidence for clinical efficacy.

The Defense Centers of Excellence for Psychological Health and Traumatic concluded that sufficient case reports, early safety and feasibility study data, and basic scientific plausibility exist to warrant prompt experimental study of HBO2 in the care of the full spectrum of chronic TBI. This would best be accomplished in a randomized, double-blind, multi-center clinical trial.

This Phase 2 study, through specific study design, inclusion and exclusion criteria, interim and end point analyses, treatment protocols, dose-response and safety issues, evaluation methodologies, safety, and outcome measures address the need for clinical efficacy.

In preparation for the pivotal trial, the purpose of this Phase II study is to describe the magnitude of change between baseline and follow-up outcomes for a battery of neuropsychological tests within groups. A secondary objective is to explore changes across the four groups. Differences and variability of the tests will be used for determining the optimum primary endpoint(s) for the Phase III trial, as well as for refinement of sample size and power calculations for this future study. Recruitment, randomization, blinding, and study and intervention logistics and planning will also be assessed.

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.