Impedance cardiography

ObjectiveElectrical 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 restrictions. In 1966 Kubicek et al. developed an impedance cardiac output system based upon electrodes and a specific stroke volume formula. In 1983 Sramek et al. developed a new electrode configuration, and a new equation to calculate stroke volume, an equation that was adjusted by Bernstein in 1986. Since then these two methods have been used in clinical medicine. The purpose of the present study was to compare both electrode configurations and both stroke volume calculation equations with each other. The cardiac output (CO) values obtained by means of EIC are compared with CO values obtained by means of thermodilution.DesignProspective study.SettingSurgical intensive care unit of a university hospital.Patients20 mechanically ventilated patients after cardiac surgery.Measurements and resultsSimultaneous measurement of CO by means of electrical impedance cardiography (COEIC) and thermodilution (COTD) was performed. COEIC was obtained using the lateral spot electrode configuration (LS) and an adjusted circular electrode configuration (SC). The formulas of Sramed (S), Sramek-Bernstein (SB), Kubicek (K) and an adjusted Kubicek formula (aK) were employed. Using the LS electrode configuration, significant differences were found between COEIC and COTD with the S formula (p<0.005), the K formula (p<0.001), and the aK formula (p<0.05). Using the SC electrode configuration, significant differences between COEIC and COTD were found with the K formula (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 electrode configuration together with the SB formula or using the SC electrode configuration with the aK formula. In both cases a good correlation was found between COEIC and COTD (r=0.86,p<0.001 andr=0.79,p<0.001, respectively). The mean difference between EIC and TD was 0.15±0.96 l/min and 0.19±1.19 l/min, respectively.

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