“With advances in medicine, the role of non-invasive methods as an alternative to pulmonary artery catheterization continues to grow.” 
Recent review article by an expert group from the Medical University of Warsaw, Poland, discussing non-invasive cardiac output measurement techniques and their application in clinical practice. As Cardiac Output is an important prognostic parameter for hemodynamic monitoring in critically ill patients, the role of non-invasive methods is increasing due to safety and availability reasons.
„Previous devices of this type were thought to be prone to measurement errors resulting from vasoactive changes. It is quite obvious that patients in intensive care units often receive large doses of vasoactive drugs which induce rapid changes in blood pressure but also affect peripheral arterial tone. CNAP monitors were designed to eliminate these limitations by employing appropriate algorithms. The CNAP 500 monitor is an independent device that can be used on its own but it may also be connected to other patient monitoring systems, providing a more comprehensive picture of the patient’s status beyond the cardiovascular system function.“ 
Cardiac output is an important parameter in the evaluation of the patients’ haemodynamic status which can be measured using a number of methods with varying degrees of invasiveness. These include invasive (such as pulmonary artery catheterization, transpulmonary thermodilution, lithium dilution), minimally invasive (catheter-based arterial pressure curve contour analysis, transoesophageal Doppler) and non-invasive (electrical bioimpedance, transthoracic echocardiography, measurement of exhaled CO2, continuous non-invasive blood pressure measurement) techniques. With advances in medicine, the role of non-invasive methods as an alternative to pulmonary artery catheterization continues to grow. The undoubted advantage of non-invasive methods is their safety for the patients and their wide availability. In contrast, invasive methods are characterized by greater measurement precision. It is up to the physician to choose the most appropriate haemodynamic monitoring method depending on the clinical situation. The aim of this article is to discuss non-invasive cardiac output measurement techniques and their application in everyday clinical practice.
Stępniak, P., Cacko, A., Kołodzińska, A., & Grabowski, M. (2021). Non-invasive methods of cardiac output measurement and their importance in everyday clinical practice : the current state of knowledge. Folia Cardiologica 2021, 16(4), 237–241. https://doi.org/10.5603/FC.2021.0036