Abstrakt
The cardiac output monitoring devices based on pulse wave analysis (PWA) became a standard of hemodynamic management in many selected patients in critical and perioperative care. They are known as "minimally invasive" because the only rerequisite is a conventional arterial catheter.
The technology is based on the arterial pressure curve (pulse wave) mathematical analysis. The PWA monitors are either calibrated or noncalibrated.
Nowadays, four different technologies/mathematical models are marketed. EV1000 with FloTrac sensor (Edwards Lifesciences, Irvine, USA) uses mathematical/statistical analysis of the arterial curve.
It derives stroke volume from small oscillations of arterial pressure values multiplied by a coefficient related to vessel impedance. PulsioFlex (Getinge, Gothenburg, Sweden) is based on dynamically changing aortic compliance, using integration of the systolic part of the arterial curve multiplied by the k constant, which is an internal factor corresponding to arterial impedance.
LiDCO Rapid (LiDCO, London, UK) uses a pulse power algorithm-the arterial pressure curve is transformed into a volume curve according to the law of conservation of energy and mass. The last device, using the pressure recording analytical method (MostCare, Vytech Health, Padova, Italy), is based on pressure curve analysis; however, unlike all the others, it also uses the diastolic part of a curve (corresponding to continual blood flow).
It calculates systemic impedance from pressure values, which are acquired at a very high frequency (1000 Hz). This chapter reviews the basic technology considerations as well as the appropriate use of these devices.