The aim of this study is the estimation of the agreement between esCCO™ and the transcardiopulmonal thermodilution technique (PiCCO®) using Bland-Altman-treatment. The 95%-confidence interval of the limits of agreement was selected for the design of the number of cases. At a number of cases by 100 you will get the width of 0,68 s (s: standard deviation of the differences of the measurement techniques). This is reasonable for the question (Bland and Altman 1986, you have to compare the recommendation of Bland: https://www.users.york.ac.uk/~mb55/meas/sizemeth.htm).