Measurement of the amount of blood pumped by the heart (cardiac output) and blood volumes in sick patients is important for doctors to better treat these patients. Current procedures available demand difficult invasive procedures and hence these parameters are not measured with enough frequency and are also limited to certain patients. The new COstatus system is capable of using the already existing arterial and venous lines placed in critically ill patients and thus provides an opportunity to measure these parameters less invasively and with enough frequency.