Fig. 5. . Receiver operating characteristics (ROC) curves representing the discriminative power of volume expansion–induced changes in PPV to detect an increase of more than 15% of cardiac output after volume expansion (A ) and two-graph ROC curves: sensitivity and specificity of volume expansion–induced changes in PPV according to the value of the cutoff for the detection of more than 15% increase in cardiac output after volume expansion. The inconclusive zone, which is more than 10% of diagnosis tolerance, is represented as a hatch rectangle (B ). AUC = area under the curve; PPV = pulse pressure variation.