Fig. 8. Systolic pressure variation (SPV) in hypovolemic, normovolemic, and hypervolemic patients. The y-axis represents the percentage of patients who had an SPV less than 10 mmHg ( black bar ) or greater than 10 mmHg ( gray bar ). This is the first study showing a link between SPV and the volemic status of critically ill patients. SPV is frequently greater than 10 mmHg in hypovolemic patients but remains below this threshold value in almost 30% of cases. CVP = central venous pressure; PAOP = pulmonary artery occlusion pressure. Adapted from Rick and Burke 4 ; used with permission.