Hemodynamic Responses and G Protection Afforded by Three Different Anti-G Systems

Area of Science:

• Aerospace Medicine
• Human Physiology
• Protective Equipment Research

Background:

• UK Royal Air Force fast jet aircrew utilize three distinct anti-G systems.
• Objective comparisons of the G-protection efficacy and physiological responses are limited.
• Understanding system performance is crucial for aircrew safety and operational effectiveness.

Purpose of the Study:

• To objectively compare the G-protection provided by three anti-G systems.
• To investigate the associated hemodynamic responses during simulated high-G exposure.
• To evaluate subjective effort required for maintaining vision under G-load.

Main Methods:

• Ten subjects underwent centrifuge acceleration exposures using Mk-10 (S1) and Mk-4 (S2) five-bladder anti-G trousers (AGT), and full coverage AGT with pressure breathing for G-protection (PBG; S3).
• Measurements included relaxed G tolerance (RGT), eye-level blood pressure (BP_eye), lower body blood volume (LBV), stroke volume (SV), and total peripheral resistance (TPR) during gradual and rapid onset runs (GOR/ROR).
• Subjective visual clarity at +7 and +8 G_z was assessed.

Main Results:

• All systems mitigated decreases in SV and BP_eye, and increases in LBV under +G_z.
• The full coverage AGT with PBG (S3) demonstrated the highest mean RGT (GOR: +6.2 G_z; ROR: +6 G_z), reduced subjective effort, prevented venous pooling, and increased TPR.
• S1 and S2 showed similar performance, with S2 offering slightly greater RGT during ROR (+0.25 G_z).

Conclusions:

• Full coverage AGT with pressure breathing (S3) effectively prevents lower limb blood pooling and offers superior G-protection compared to five-bladder AGT.
• Objective hemodynamic measurements provide valuable data for comparing anti-G system effectiveness.
• The study highlights the benefits of advanced anti-G systems for high-G environments.