The Effects of Transport Altitude on Outcomes in Traumatic Brain Injury (HEIGHT-TBI): An Observational Cohort Study

Traumatic brain injury (TBI) that is more than minor frequently requires aeromedical transport to higher-level trauma centers. The detrimental effects of hypoxemia and hypotension during transport are well established, but the influence of transport altitude and ambient barometric pressure on patient outcomes remains poorly understood. This study aimed to evaluate whether transport altitude is associated with in-hospital mortality in adults with more than minor TBI.

We performed a retrospective cohort study of adult patients (≥ 18 years) with more than minor TBI (Abbreviated Injury Scale-Head [AIS Head] score > 1) transported by air between January 2017 and December 2023. Data sources included state trauma databases, hospital electronic medical records, and regional flight transport company records. Transport altitude was categorized as ≤ 1500 ft, 1500-3000 ft, 3000-6000 ft, and > 6000 ft. Multivariable logistic and negative binomial regression analyses were conducted to examine associations between altitude, clinical variables, and outcomes, adjusting for confounders such as age, sex, injury severity, in-flight hypotension, and transport duration. Primary outcomes were all-cause in-hospital mortality and hospital disposition. Secondary outcomes included hospital and intensive care unit (ICU) admission rates and length of stay (LOS).

The cohort included 1135 flights involving 1132 individual patients (mean age 53.6 years; 69.6% male). Flights above 6000 ft were associated with higher in-hospital mortality (adjusted odds ratio [aOR] 4.88; 95% confidence interval [CI] 1.26-18.94) compared with ≤ 1500 ft. In-air hypotension was independently linked to increased mortality (aOR 4.26, 95% CI 2.22-8.19) and discharge to a care facility (aOR 3.45, 95% CI 2.03-5.87). Longer transport times were paradoxically associated with a slight reduction in mortality (aOR 0.97, 95% CI 0.95-0.99). Transport altitude did not significantly affect hospital or ICU LOS.

Transport above 6000 ft and in-flight hypotension are associated with increased in-hospital mortality among patients with more than minor TBI. These findings underscore the need for further research on the physiological impact of hypobaric aeromedical transport and the development of mitigation strategies to optimize patient outcomes.