[Potential for modelling the hemodynamic effects of weightlessness by exposure to increased pressure]

Venous and arterial circulation was investigated by simulating cephalad blood shifts generated by an exposure of test subjects (n = 15) to lower body positive pressure (+25 mm Hg) and head-down tilts (at -8 degrees and -15 degrees). At LBPP and tilt -15 degrees arterial pressure increased by 5-15%. During tilt -8 degrees jugular vein blood filling increased by 8-94% in the course of the first 3 hrs and then decreased reaching the baseline (horizontal position) level. During LBPP the parameter changed in a similar manner (increased by 2-50%). During tilt -15 degrees the parameter grew by 10-110% and remained elevated. The exposures gave rise to bradycardia which was more pronounced during -8 degrees and LBPP. The data obtained give evidence that circulation changes during LBPP and head-down tilts are identical. This suggests that LBPP can be used to simulate the effect of cephalad blood shifts, one of the most important effects of weightlessness on the human body.