A unique model for noninvasively estimating cardiac output and cardiac output trends over time

An analog circuit model has been developed to compute cardiac output using a single noninvasive displacement transducer located at the superficial carotid artery. The LICO model (Local Impedance, Compliance and Output model) is driven by a step input of pressure equal to the pulse pressure. The timing of the resulting flow is determined from the carotid pulse contour. A study of 102 records from cardiac surgery patients shows that 84% of the records yield cardiac outputs that agree within 20 percent of thermodilution. An important finding is the strong ability of the LICO system to track changes in cardiac output over time. Multiple trials, with time intervals between 5 minutes and 24 hours, were recorded post-surgically in 10 hemodynamically unstable patients. During this time, the LICO model tracked trends in cardiac output as estimated by thermodilution in all the patients, and matched magnitudes for 90 percent of the patients. This suggests a clinical application for cardiac output monitoring after the Swan-Ganz catheter is removed