The cardiac output (CO) is an important parameter in the diagnosis and therapy of cardiac diseases. The current standard methods for the determination of the CO, however, are either invasive (e.g. right heart catheterization) or technically expendable and expensive (magnetic resonance tomography, MRT). Therefore the aim of the study at hand was to evaluate the electrical velocimetry technique as a new method for determining the CO and to compare this new technique with the Inert Gas Rebreathing Method and with the Magnetic Resonance Tomography