Impedance Cardiography for Determination of Cardiac Output and its Correlation with Thermodilution

pp 595-600

Abstract

Background We present the development of an impedance cardiograph for the cardiac output estimate and its correlation with the thermo dilution method.Material and method A constant electrical flow of 50 KHz frequency and of 1.5 to 3 mA amplitude is passed through a senoidal source. We carried out an appraisal of method recurrence in healthy people. A Swan-Ganz catheter was placed in a group of 31 patients and basal, inotropic and betablocker stimulation was performed. Kubiceck and Srameck formulas were used to estimate the cardiac output. Results Recurrence evaluation: a variation up to a 30%in the cardiac output was observed in different days of estimation. Comparison to the thermodilution method: a) with the Kubiceck equation (17patients) correlation coefficients in basals 0.72, after inotropics 0.92 and after betablockers 0.94; b) comparison with Srameck formula (14patients) basal correlation coefficients0.17and after inotropics 0.32. Conclusions The method has many sources of errors, therefore it's very difficult its clinical application now, both in the follow up of the cardiac output changes in absolute values and the relative variation in percentage count, but in this last point it's necessary the confirmation with more patients and differents electrodes types.