In-Flight Assessment of Simulated Hemorrhage During Aerial Patient Evacuation

Area of Science:

• Aerospace Medicine
• Human Physiology
• Emergency Medicine

Background:

• Understanding flight impacts on hemodynamically unstable patients is crucial for aerial evacuation survival.
• This study integrated an experimental model of hemorrhage in an aircraft during evasive maneuvers.

Purpose of the Study:

• To assess the physiological responses of healthy humans to simulated hemorrhage during various flight trajectories.
• To quantify the impact of acceleration and blood loss on cardiovascular decompensation during casualty evacuation.

Main Methods:

• Nine volunteers underwent incremental lower body negative pressure (LBNP) to simulate hemorrhage in a C-12J aircraft.
• Physiological monitoring and environmental sensors recorded data during wind-up turns, roller coasters, and acceleration/deceleration maneuvers at 5500-9500 ft.
• LBNP was incrementally applied from 0-60 mmHg, simulating mild to severe hemorrhage.

Main Results:

• Flights included wind-up turns (up to 1.93 Gx), roller coasters (0.4-2.8 Gx transitions), and level acceleration/decelerations (-0.1-0.3 Gz).
• Gx acceleration was driven by low-frequency aerodynamics, while lateral forces resulted from high-frequency mechanical inputs.
• Data captured reductions in Gx-tolerance and increased vibration between healthy and simulated hemorrhage states.

Conclusions:

• An in-flight experimental setup was established to study healthy and hemodynamically unstable patients.
• The method allows independent titration of LBNP and G-forces to establish dose-response relationships.
• This provides crucial human data to understand cardiovascular decompensation mechanisms in aerial patient evacuation.