Fig. 3. Receiver operating characteristic (ROC) curves comparing the capacity of various variables to discriminate between fluid responders and nonresponders. The ROC curves are derived from six diagnostic parameters used to assess fluid responsiveness: (A) baseline-1 TVC PPV, the PPV during ventilation with a tidal volume of 6 mL/kg predicted body weight; 8 mL TVC-PPV, the PPV during ventilation with a tidal volume of 8 mL/kg predicted body weight; ΔPPV6-8, the change in PPV upon transition from 6 to 8 mL/kg predicted body weight tidal volume. (B) Baseline-1 TVC SVV, the SVV during ventilation with a tidal volume of 6 mL/kg predicted body weight; 8 mL TVC-SVV, the SVV during ventilation with a tidal volume of 8 mL/kg predicted body weight; and ΔSVV6-8, the change in SVV upon transition from 6 to 8 mL/kg predicted body weight tidal volume. TVC, tidal volume challenge; PPV, pulse pressure variation; SVV, stroke volume variation.