Evaluation of Neurophysiologic and Systematic Changes during Aeromedical Evacuation and en Route Care of Combat Casualties in a Swine Polytrauma
Technical Report,15 Jan 2015,14 Jan 2016
Henry M. Jackson Foundation Bethesda United States
Pagination or Media Count:
There is a dearth of knowledge about the effects of long range aero-medical evacuation on injured organs, as well as an emerging published database suggesting clinically significant adverse effects of hypobaria on even healthy tissues. Cabin pressure is equivalent to an altitude around 8,000ft. at which inspired oxygen is sufficient to maintain blood oxygen saturation above 90 in a healthy individual. In combat casualties with multiple injuries this could however compromise oxygen delivery and result in hypoxemia. Additionally, increase in altitude with concomitant decrease in atmospheric pressure allows gas expansion in body cavities. The volume of trapped gas expands by approximately 35 from sea level to an altitude of 8,000 feet. This can expose already vulnerable patients to severe complications. In light of this, a thorough investigation of the effects of hypobaria in clinical settings simulating the most important injury patterns encountered by combat casualties is necessary to optimize treatment efficacy and safety.During the third year of this project, experiments in swine with Acute Respiratory Distress Syndrome ARDS and with Traumatic Brain Injury TBI have been completed and results have been presented at National Scientific Meetings. We found that a simulated four hour aeromedical evacuation flight in those models significantly reduced arterial oxygen pressure and increased intrapulmonary shunt fraction in ARDS and significantly reduced cerebral perfusion pressure and brain tissue oxygenation in TBI compared to normobaric conditions. Further studies are indicated to simulate other en route care scenarios and possibly revise casualty evacuation guidelines.