Mathematical modeling of high G protection afforded by various anti-G equipment and techniques

It is difficult to assess how different combinations of recently developed anti-G protective equipment will affect +Gz tolerance and central hemodynamics during high G solely by centrifuge experiments. In this paper we report a mathematical model simulating the effects of various combinations on human circulatory response and +Gz tolerance, and its validation with published centrifuge data.

A structurally based mechanistic model incorporating cardio-pulmonary function, as well as a more detailed modeling of vessel segments for different anatomic regions, was established to simulate hemodynamic responses during high-G exposure and the protection afforded by various protective modalities, such as tilt-back seats, extended coverage anti-G suits (ECGS), and positive pressure breathing for +Cz (PBC).

There were 43 pairs of human data from centrifuge trials and model outputs under the same or similar conditions that were compared. This comparison indicated that in 86% of cases the differences were less than 15%. From the model outputs, the best combinations which satisfied different protective needs, such as protection to +9 Gz, +10 Gz, and +12 Gz, respectively, could be discovered. They also suggested that while the combined protection of ECGS with PBG may be expressed as a simple addition of the two effects, the combined effect of the tilt-back seat with ECCGS and/or PBG seemed to be better fitted by a synergistic model.

Comparisons with published centrifuge data have suggested the validity and confidence of the model developed. The benefits and limitations of the model for future high-G physiology and protection are discussed.