Cardiac output is an important parameter in the assessment of cardiac performance in patients with heart disease. The gold standard for exact determination is examination during a cardiac catheterization. This invasive measurement procedure is used in children in preparation for heart transplantation and in cases of severe heart failure, for example in the context of inflammatory diseases of the heart muscle (myocarditis or cardiomyopathy). However, catheterization in children cannot always be justified as a routine examination to assess cardiac output due to its invasiveness.
With the non-invasive, less stressful Innocor method, which can be repeated as often as required, the analysis of cardiac output is based on the rebreathing method with inert gases: The blood-insoluble sulphur hexafluoride and the blood-soluble nitric oxide N₂O percent are added to the breath via a photoacoustic gas analyzer. The washout of N₂O can be used to draw direct conclusions about the cardiac output via the blood flow in the lungs. The examination only takes a few minutes and requires five breaths through a mouthpiece to empty the rebreathing bag filled with the respiratory gases, similar to a lung function test.