In-Flight Assessment of Simulated Hemorrhage During Aerial Patient Evacuation

Understanding how flight trajectories impact hemodynamically unstable patients is critical for maintaining high survival rates during aerial evacuation. We integrated an experimental model of hemorrhage in an aircraft during evasive maneuvers to capture the physiological response in healthy humans vs. simulated hemorrhage.

Lower body negative pressure (LBNP), a validated method to simulate hemorrhage, and continuous physiological monitoring were integrated into a C-12J aircraft. Nine volunteers underwent incremental LBNP during wind-up turns, roller coasters, and level acceleration/deceleration trajectories at cabin pressure altitudes of 5500-9500 ft (1670-2890 m). Environmental sensors recorded acceleration, vibration, temperature, and pressure.

Nine sorties totaling 27.5 flight test hours were completed. Wind-up turns produced Gx accelerations of 1.21 ± 0.09 G (mean ± SD), 1.47 ± 0.06 G, and 1.93 ± 0.10 G, with additional Gz (0.05-0.18 G). Roller coasters produced rapid Gx transitions between 0.4-2.8 G. Level acceleration/decelerations generated -0.1-0.3 Gz. Incremental LBNP was applied from 0-60 mmHg, simulating mild, moderate, and severe hemorrhage. Gx was driven by low-frequency aerodynamics; lateral by high-frequency mechanical inputs.

We have, for the first time, established a real-world in-flight experimental set-up to conduct direct crossover trials and capture the reductions in Gx-tolerance and vibration between healthy and hemodynamically unstable patients. Our method allows us to titrate LBNP level (degree of hemorrhage) and G-forces independently, thus providing a tool to understand both isolated and synergistic impact of acceleration and blood-loss to establish dose-response relationships. Our method provides important human data to directly quantify the delta between healthy human and simulated trauma (hemorrhage) to better understand the underlying mechanisms of cardiovascular decompensation in casualty evacuation. Tibbs ML, Lee C, Morse BG, Romero E, Petersen LG. In-flight assessment of simulated hemorrhage during aerial patient evacuation. Aerosp Med Hum Perform. 2026; 97(2):123-130.