Receiver operating characteristic (ROC) curves were constructed to evaluate the ability of ΔRESPPP, ΔRESPPP/DP, CVP and PAOP to predict fluid responsiveness. The best cut-off value for ΔRESPPP ROC curve was determined for the entire population. In addition, measures of diagnostic performance were calculated: sensitivity, specificity, predictive values and likelihood ratio. Linear correlations were tested using the Spearman rank method. Data were analyzed using SPSS 15.0. A p value <0.05 was considered significant.