The monitoring of the cardiac output (CO [l/min]) is usually carried using various dilution methods.
The one most commonly used in clinical routine is thermodilution thanks to its relatively easy application and repeatability.
Unfortunately this method is unsuitable in instable haemodynamic, extremely hyperdynamic, or hypodynamic conditions as is normally the case in a critical patient.
It is therefore precisely in these clinical sectors where the CO monitoring is so vital that thermodilution is liable to give rise to problems for technical reasons or due to the theory of the method (necessity of a stable flow, etc).
It often happens that apart from not providing CO values linked to the rapid haemodynamic variations (pathological and/or pharmacological), it may also create discomfort for the patient as a result of the high invasiveness required.
The continuous, beat-to-beat monitoring of the CO may represent an extremely useful parameter for assessing the heart conditions, and therefore play a fundamental role in diagnostics and clinical medicine.
This explains why such a great number of methods have been applied, especially over recent years.