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. Author manuscript; available in PMC: 2022 Mar 5.
Published in final edited form as: Clin Auton Res. 2019 Mar 5;29(2):215–230. doi: 10.1007/s10286-019-00598-9

Figure 1.

Figure 1

Schematic diagram of the head-up tilt table test. The blue shape represents an approximation of the distribution of the central venous blood volume, which at a baseline angle of 0° is liberally present in the thorax. At at an angle of 70° the force of gravity shifts much of the thoracic venous blood volume downward into the pelvis and proximal lower extremities. A tilt angle of 70° results in a gravitational force of 0.94 G, which approximates the vertical angle but does fully engage the leg muscles to remain upright.