HBOT Effects on First Responders' Cognition and Well-Being

Inclusion criteria 1. Adults aged 18 to 75 years. 2. Current or former first responder. 3. Clinically diagnosed with a traumatic brain injury (TBI) and current or persistent post-concussive syndrome, as determined by a qualified health care professional. 4. Participants with comorbid PTSD, depression, or anxiety may be enrolled if all other eligibility criteria are met; these symptoms will be assessed as secondary/exploratory outcomes. 5. Ability to provide informed consent, including the ability to read, understand, and voluntarily sign the informed consent document. 6. Completion of baseline cognitive and psychological assessment measures as part of study enrollment procedures. 7. Presence of clinically significant symptoms resulting in functional impairment in occupational, social, or other key areas of functioning, as determined by clinical evaluation. 8. Sexually active female participants of childbearing potential and sexually active male participants with female partners of childbearing potential must agree to use an acceptable method of contraception for the duration of the study and for 30 days following the final HBOT session. 9. Stable regimen of psychoactive medications (if applicable), including antidepressants, anxiolytics, antipsychotics, stimulants, and mood stabilizers, for a clinically appropriate stabilization period prior to enrollment, as determined by the study physician. Exclusion criteria 1. Untreated pneumothorax 2. History of spontaneous pneumothorax 3. Severe sinus infection 4. Upper respiratory infection 5. Asymptomatic pulmonary lesions on chest x-ray 6. Uncontrollable high fever (greater than 39C) 7. History of chest or ear surgery 8. Congenital spherocytosis 9. Any anemia or blood disorder 10. Any convulsive disorder 11. History of optic neuritis or sudden blindness 12. Middle ear infection 13. Diabetes mellitus (insulin therapy) 14. The participant is pregnant or lactating 15. Nicotine use/substance use/addiction 16. Acute Hypoglycemia 17. Diagnosed Chronic Obstructive Pulmonary Disease (COPD) and Emphysema 18. Presenting with symptoms of cough, congestion, vomiting, diarrhea, or open wounds. 19. Active malignancy 20. Current manic, delusional, or psychotic episodes 21. Serious/current suicidal ideations 22. Severe or unstable physical disorders or major cognitive deficits 23. Inability to attend scheduled clinic visits or comply with study protocols. 24. Treated with HBOT for any reason prior to study enrollment. 25. Non-English speakers 26. History of retinal repair, including laser photocoagulation or retinal detachment surgery. 27. History of middle ear surgery, including tympanoplasty, mastoidectomy, or pressure equalization tube placement. 28. Age greater than 75 years. 29. Use of any of the following medications during the study period: Anti-metabolites (e.g., methotrexate, azathioprine); Chemotherapuetic agents (e.g., cyclophosphamide, cisplatin); Mafenide acetate e.g., Sulfamylon); Disulfiram (e.g, Antabuse); Peripheral vasodilators known to interact with oxygen exposure (e.g., nitroglycerin); and Antibacterial drugs with known HBOT interaction risks.