Comparison of Cardiac Output Measurement Techniques: Thermodilution Versus Biventricular Pressure-Volume Loop Recordings in Pigs

Cardiac output (CO) measurement is crucial in cardiovascular research. Pressure-volume (PV) loop recordings provide detailed information on cardiac function, including CO. This study aimed to compare CO measurements obtained from biventricular PV loop recordings with thermodilution (TD) as a reference method in pigs. The TD-CO was measured by right heart catheterisation. The PV-derived CO was obtained from both ventricles simultaneously, both during ongoing ventilation and in transient apnoea. Data were compared using the Bland-Altman method. The percentage error (PE%) and linear regression were calculated between the TD-CO and PV-derived CO. Simultaneous CO measurements from 43 pigs were analysed. Compared to thermodilution, the lowest bias was found in PV-derived CO from the left ventricle during ongoing ventilation (0.02 L/min, 95% confidence interval [0.2-0.3]) with a PE% of 30% during ongoing ventilation. The highest bias was found in PV-derived CO from the right ventricle during ongoing ventilation (0.9 L/min, 95% CI [0.5-1.3]) with a PE% of 67% during ongoing ventilation. PV-derived CO from the left ventricle showed very good agreement with TD-CO, with minimal bias, while PV-CO measurements from the right ventricle showed higher inaccuracy, likely due to anatomical differences between the ventricles.