Persistent post-concussive symptoms (PPCS) are a source of significant burden among a subset of patients with concussion with prevalence rates previously reported between 11 - 82% based on timing of assessment, diagnostic criteria, or population under study.

Examples of persistent post-concussion symptoms include balance problems, headaches, fatigue, poor concentration, forgetfulness, anxiety, irritability, and sleep disturbance. Few proposed therapies have proved successful in the management of persistent post-concussion symptoms following mild traumatic brain injury.

The investigators will explore hyperbaric oxygen administered in a randomized sham-controlled clinical trial as an effective and tolerable treatment in improving neuropsychological status among adult patients with persistent post-concussive symptoms.

The overall hypothesis to be evaluated is that hyperbaric oxygen improves neuropsychological status and a serum concussion biomarker associated with PPCS.

This is a parallel, randomized, double-blinded and sham-controlled study. A total of 100 subjects will be randomly assigned to either an intervention arm: 50 participants exposed to > 99.9% oxygen at 1.5 atmosphere absolute for 60 minutes over 40 treatments or sham-treatment arm: 50 participants exposed to oxygen and pressure composition equivalent to breathing atmospheric air for 60 minutes over 40 treatments.

This study is designed to determine whether hyperbaric oxygen improves neuropsychological status and ameliorates symptoms in adults with persistent post-concussive symptoms (PPCS) following mild traumatic brain injury. It recruits from either military or civilian population; uses a validated screening tool - Repeatable battery for the assessment of neuropsychological status (RBANS)- used in dementia and other forms of brain injury not used hitherto, in previous randomized control trial that investigated the effectiveness of hyperbaric oxygen in the management of PPCS. It also includes a concssuon biomarker, as an objective secondary endpoint.

The study is based on repeated measure design. The study will describe and track changes in the outcomes of interest over time, and examine associations between measures within each participant and across certain participant characteristics.

Inclusion Criteria:

• Volunteers must have a history of mild traumatic brain injury, specifically, persistent post-concussive symptoms after examination by a neuropsychologist or neurologist.
• Volunteers time from concussive incident (Mild traumatic brain injury) must be between 3 months - 5 years following head trauma incident
• TBI was caused by non-penetrating trauma
• Volunteers must have current complaints of TBI symptoms such as headache, dizziness, or cognitive or affective problems
• Volunteers must be 18-year-old or more
• Willing and able to provide informed consent
• Able to speak and read English, as primary language
• Agrees to provide blood samples for clinical lab tests
• Willing and committed to comply with research protocol and complete all outcome measures
• Able to equalize middle ear pressures or willing to undergo needle myringotomies if needed
• Willingness and committed to comply with study protocol outlined reproductive plan based on baseline reproductive status

Exclusion Criteria:

• Prior treatment with hyperbaric oxygen treatment
• Hyperbaric chamber inside attendant, professional, SCUBA diver (technical, commercial, operational/military or recreational)
• The investigators will exclude pregnant women from this study because potential fetal adverse reactions triggered by high oxygen partial pressures such as retrolenticular fibroplasia though careful review of human data are generally reassuring such as the use of hyperbaric oxygen to treat acute carbon monoxide poison in the pregnant patient.13
• Prisoners
• Minors
• Unable to protect airway or requires frequent suctioning
• Known or suspected peri-lymphatic fistula
• Presence of tracheostomy (due to limitations in auto-inflating the middle ear)
• Unable to participate fully in outcome assessments
• Unable to cooperate with hyperbaric oxygen treatments
• Unable to speak and read English, as primary language
• Not cooperating with instructions during hyperbaric oxygen treatments such as bringing contraband items into the chamber (such as fire lighter)
• Not competent to sign their own consent. Such potential participants will not have the capacity to participate in a full range of neurocognitive testing
• Pre-existing diagnosis of a psychotic disorder(s): schizophrenia, bipolar, dissociative disorder
• History of moderate or severe traumatic brain injury
• History of brain injury not of traumatic etiology such as stroke or drug-induced coma
• Verifiable diagnosis of learning disability. Other pre-existing cognitive issues may make it difficult for potential participants to fill out certain outcome assessments such as neurobehavioral symptomatic inventory. This could lead to measurement bias or confound the result.
• Claustrophobia and unwilling to enter hyperbaric chamber
• Untreated pneumothorax
• Presence of implanted device with un-verifiable test to pressure by manufacturer
• Concurrent enrollment in an alternate interventional trial for post concussive symptoms

The study protocol, statistical plan and consent form will be available on request. Data will be available on aggregate level; data will be deidentified, the full dataset and statistical code will be available upon request

6 months after study completion and for 36 months

A full description of the intended use of the data must be sent to the corresponding author for review and approval. Participant consent for data sharing is conditioned and new ethics approval may be required.