Estimation of Hemodynamic Parameters by Arterial Waveform: Available Technologies

Abstract

To the Editor: Funk et al.1 present an interesting review concerning new minimally invasive technologies and devices available for measurement of cardiac output. In their review, Funk et al. did not consider 2 systems: the first is the Modelflow by Wesseling and co-workers2 installed on the Finometer® (Finapres Medical Systems, Amsterdam, The Netherlands); the second is the Pressure Recording Analytical Method (PRAM; used by MostCare®, Vytech Health, Padova, Italy) by Romano et al.3,4 “Pulse contour methods” (PCMs) can be divided into 3 categories: PCMs requiring an indicator dilution cardiac output measurement to calibrate the pulse contour; PCMs requiring patient demographic and physical characteristics for arterial impedance estimation; PCMs that work without any kind of calibration or preloaded data. The PRAM is the only methodology belonging to category 3 because neither calibration nor adjustments based on experimental data are required.3–5 Therefore, PRAM is different than all the other PCMs including the more recent Flo Trac Vigileo® (Edwards LifeSciences, Irvine, CA) and LiDCOrapid™ (LiDCO Ltd, London, UK), which require preloaded patient's demographic and physical characteristics (age, height, gender, and weight), similar to Modelflow6,7 (category 2). For PRAM, the area under the systolic portion of the arterial wave is computed by considering both pulsatile and continuous contributions (Acp). Stroke volume derives from the ratio between Acp and the arterial impedance Z(t) that is directly determined from the detailed analysis of the arterial wave sampled at high frequency (1000 Hz).3 Stefano Romagnoli, MD Heart and Vessels Department Cardiac and Vascular Anesthesia and Post-Cardiac Surgery Intensive Care Unit Careggi Hospital Florence, Italy [email protected] Salvatore Mario Romano, PhD Heart and Vessels Department Critical Care Medicine and Surgery University of Florence Careggi Hospital Florence, Italy