title: Mathematical modeling of high G protection afforded by various anti-G equipment and techniques.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Computer Application, The Fourth Military Medical University, Xi'an, China.
authors.forename: Hong-Bing
authors.initials: HB
authors.lastname: Lu
authors.forename: Li-Fan
authors.initials: LF
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Bai
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Guo-Peng
authors.initials: GP
authors.lastname: Zhang
mesh_terms: D001775:Blood Circulation / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D002498:Centrifugation; D003198:Computer Simulation; D004867:Equipment Design; D005676:Gravity Suits; D006339:Heart Rate; D006801:Humans; D008954:Models, Biological; D008955:Models, Cardiovascular; D011187:Posture / Q000502:physiology; D012143:Respiratory Physiological Phenomena