Hypobaria during aeromedical evacuation exacerbates histopathological injury and modifies inflammatory response in rats exposed to blast overpressure injury

BACKGROUND Aeromedical evacuation (AE) is often used as a rapid and effective way to evacuate patients. However, little is known about the possible effects of AE on patients with blast and traumatic brain injury. In the current study, we used blast overpressure (BOP) as a method to introduce traumatic brain injury in rats and investigated the effects of hypobaria during AE on histology and inflammatory response. METHODS Animals were exposed to a 12-hour flight 2 days after BOP and euthanized 48 hours after flight. Control animals were kept at normobaria. RESULTS Overall, BOP animals exposed to flight demonstrated higher histopathologic injury scores as compared to control animals in lungs, brain, kidney, heart, and intestine. The BOP animals exposed to normobaria exhibited a proinflammatory response compared to those that were not blasted, an observation that was not seen in BOP animals exposed to hypobaria. CONCLUSION These data suggest that AE 48 hours post blast may lead to impairment in the inflammatory process and worsening of long-term outcomes. LEVEL OF EVIDENCE Animal research, level II.