Figure 3. Correlation between superior vena caval pressure (SVCP) and intracranial pressure (ICP) with the head 3+/-1 cm above the level of the right atrium (i.e., "neutral position"). There was a significant correlation between superior vena caval pressure and intracranial pressure (N = 35 data pairs collected in six dogs; r = 0.85; P < 0.001), however, the derived regression line (intracranial pressure = 0.54 superior vena caval pressure + 13) had a slope that was less than unity. This implies that only a portion of the superior vena caval pressure increase was transmitted to the head.