IMPEDANCE CARDIOGRAPHY - IMPORTANCE OF THE EQUATION AND THE ELECTRODECONFIGURATION

Objective: Electrical impedance cardiography (EIC) has been suggested as a non-invasive method to measure cardiac output. In several studies it proved to be a reliable method, although there were some restricti ons. In 1966 Kubicek et al. developed an impedance cardiac output syst em based upon electrodes and a specific stroke volume formula. In 1953 Sramek et al. developed a new electrode configuration, and a new equa tion to calculate stroke volume, an equation that was adjusted by Bern stein in 1986. Since then these two methods have been used in clinical medicine. The purpose of the present study was to compare both electr ode configurations and both stroke volume calculation equations with e ach other. The cardiac output (GO) values obtained by means of EIC are compared with CO values obtained by means of thermodilution. Design: Prospective study, Setting: Surgical intensive care unit of a universi ty hospital. Patients: 20 mechanically ventilated patients after cardi ac surgery Measurements and results: Simultaneous measurement of CO by means of electrical impedance cardiography (COEIC) and thermodilution (COTD) was performed, COEIC was obtained using the lateral spot elect rode configuration (LS) and an adjusted circular electrode configurati on (SC), The formulas of Sramek (S), Sramek-Bernstein (SE), Kubicek (K ) and an adjusted Kubicek formula (aK) were employed. Using the LS ele ctrode configuration, significant differences were found between COEIC and COTD with the S formula (p < 0.005), the K formula (p < 0.001), a nd the aK formula (p < 0.05). rising the SC electrode configuration, s ignificant differences between COEIC and COTD were found nith the K fo rmula (p<0.005), the S formula (p<0.01), and the SB formula (p<0.05). No significant difference was found between EIC and TD using the LS el ectrode Configuration together with. the SE formula or using the SC el ectrode configuration with the aK formula, In both cases a good correl ation was found between COEIC and COTD (r = 0.86, p < 0.001 and r = 0. 79, p < 0.001, respectively. The mean difference between EIC and TD wa s 0.15+/-0.961/min and 0.19+/-1.19 l/min, respectively.