Fig. 3

Receiver operating characteristic (ROC) curves during head-up tilt for systolic pressure variation (SPV) with the four different respiratory resistors. Area under the ROC curve 0.43 (0.10; 0.77 ) (confidence interval) for no resistor, 0.67 (0.25 ;1.00) for the inspiratory resistor, 0.70 (0.37; 1.00) for the expiratory resistor, and 0.96 (0.86; 1.00) for the combined inspiratory and expiratory resistor