The planed clinical trial deals with the evaluation of different methods (invasive vs. non-invasive) to measure cardiac output and other parameters. For interpretation purpose the method of Bland and Altman will be used to calculate the average deviation (bias) and precesion (mean value ± 2 standard deviations). The mean percentage error will be determined in accordance to the criteria described by Critchley and Critchley. The Bland-Altman analysis will be expanded by repeated measurements per patient and point in time.