Fig. 3

Scatterplot of individual values for the collapsibility index of the inferior vena cava (cIVC). Scatterplot of individual values before volume expansion (VE) for cIVC measured at 4 cm caudal to the IVC–atrial junction in spontaneous breathing patients, both without (a, cIVC-ns 4) and with (b, cIVC-st 4) standardized breathing manoeuvre, in non-responders and responders to VE. Red lines show the optimal threshold value for predicting fluid response