Comparison of electrical velocimetry and thermodilution techniques for the measurement of cardiac output

Abstract

Aim: To compare a new method of non‐invasive determination of cardiac output based on electrical velocimetry (EV‐CO) with invasive thermodilution methods. Methods: Fifty critically ill patients were enrolled into the study. EV‐CO was compared with cardiac output measured by a pulmonary artery catheter (PA‐CO) in one group (n= 25) and by a femoral artery catheter (PiCCO‐CO) in a second group (n= 25), by simultaneous measurements. Standard electrocardiography electrodes were used for non‐invasive measurements, and EV‐CO was calculated using the Bernstein–Osypka equation. The invasive measurements of PA‐CO and PiCCO‐CO were made by the injection of iced 0.9% saline and the recording of thermodilution curves. Results: The precision values of EV‐CO, PA‐CO and PiCCO‐CO measurements were ± 0.46 [95% confidence interval (95% CI), ± 0.06], ± 0.57 (95% CI, ± 0.09) and ± 0.48 l/min (95% CI, ± 0.08 l/min), respectively. The mean differences between EV‐CO and PA‐CO or PiCCO‐CO were –0.05 ± 0.71 and 0.22 ± 0.78 l/min, respectively. The lower and upper limits of agreement for the comparison of EV‐CO with PA‐CO were −1.47 and 1.37 l/min (95% CI, ± 0.25 l/min), respectively. In the comparison of EV‐CO and PiCCO‐CO, lower and upper limits of –1.34 and 1.78 l/min (95% CI, ± 0.27 l/min) were found. The percentage errors between EV‐CO and PA‐CO or PiCCO‐CO were 26.5% and 26.4%, respectively. Conclusions: The values of cardiac output were statistically comparable between the groups. Therefore, electrical velocimetry is a suitable method to evaluate haemodynamic variables with clinically acceptable accuracy.