Traumatic Brain Injury and Effects of Altitude - Human Performance ...

Traumatic Brain Injury (TBI) and Effects of Altitude:An Analysis of the Literaturedeployed to high-altitude mission environments such as Afghanistan. It is not clear whether, or how, reexposureto high-altitude settings might affect these individuals’ physical and cognitive performance.There is a pressing need for additional research in this area, given previous evidence that persistingeffects of even minor head injury may cause subtle but persistent cognitive deficits that can emergeunder mildly hypoxic conditions. Ewing et al. (1980) observed vigilance and memory decrements inpreviously concussed (vs. non-concussed) individuals when exposed to simulated high altitude (3800meters). In addition, preliminary data suggests that individuals with disabilities performing as athletes athigh altitude (> 2500 meters) may be more susceptible to AMS, with fatigue and weakness being themost common symptoms (Dicianno et al., 2008). The study included military personnel with a variety ofdisabilities, including paraplegia, tetraplegia, multiple sclerosis, and TBI. The incidence of AMS amongdisabled soldier athletes was not significantly different for those with neurological (vs. non-neurological)disabilities, which raises the concern that prior significant injury in general may be a risk factor for thosewho return to duty at high altitude.ObjectivesThe mission of the Defense Centers of Excellence (DCoE) for Psychological Health and Traumatic BrainInjury is to assess, validate, oversee, and facilitate the prevention, resilience, identification, treatment,outreach, rehabilitation, and reintegration programs for psychological health and traumatic brain injuryto ensure the Department of Defense meets the needs of the nation’s military communities, warriorsand families. In keeping with these objectives, DCoE requested a review and analysis of recent researchto inform the care and treatment of military TBI in high-altitude settings. The overarching intent of thisreview is to address the question of how altitude-related factors might complicate or confound militaryTBI or its care and treatment. Core concerns of this analysis are (1) the acute stages of care, when theinjured brain is most vulnerable to environmental effects associated with altitude and (2) whetherexposure to high altitude may compromise the neurological health or performance of those who returnto duty after recovering from TBI.Our analysis was focused to address three component questions:1. How is TBI affected by altitude and related/co-occurring changes in oxygenation, intra-cranialpressure (ICP), edema, temperature, blood pressure or fluid balance?2. How can altitude-related effects on the brain inform the transport, care and treatment of TBI inmilitary settings?3. Do altitude-related effects on TBI vary by injury severity level and/or acute vs. chronic injuryphase?To address these questions, we conducted a broad search of the medical scientific literature relevant toTBI, altitude-related illness, and secondary brain injury. In addition, we also performed a targetedsearch using Google Scholar and PubMed to capture clinical studies published in English within a 10-yearperiod from 2000 to April, 2010, inclusive. We used any combination of the primary search terms;traumatic brain injury, TBI, mild traumatic brain injury, mTBI, moderate TBI, severe TBI, concussion,repeat concussion, multiple concussion, and blast injury in any combination with the secondary searchterms; altitude, high altitude cerebral edema, HACE, brain volume, aeromedical, temperature,September 14, 2010 13