Simultaneous comparison of thoracic bioimpedance and arterial pulse waveform-derived cardiac output with thermodilution measurement

Objective: To compare the accuracy and reliability of thoracic electrical b ioimpedance (TEB) and the arterial pulse waveform analysis with simultaneou s measurement of thermodilution cardiac output (TD-CO) in critically ill pa tients. Design: Prospective data collection. Setting: Emergency department and critical care unit in a 2,000-bed inner-c ity hospital. Patients: A total of 29 critically ill patients requiring invasive hemodyna mic monitoring for clinical management were prospectively studied. Interventions: Noninvasive cardiac output was simultaneously measured by a TEE device and by analysis of the arterial pulse waveform derived from the finger artery. Invasive cardiac output was determined by the thermodilution technique. Measurements and Main Results: A total of 175 corresponding TD-CO and nonin vasive hemodynamic measurements were collected in 30-min intervals. They re vealed an overall bias of 0.34 L/min/m(2) (95% confidence interval, 0.24-0. 44 L/min/m(2); p < .001) for the arterial pulse waveform analysis and of 0. 61 L/min/m(2) (95% confidence interval, 0.50-0.72 L/min/m(2); p < .001) for the TEE. In 39.4% (n = 69) of all measurements, the discrepancy between ar terial pulse waveform analysis and To-so was >0.50 L/min/m(2). The discrepa ncies of the arterial pulse waveform analysis correlated positively with th e magnitude of the cardiac index (r(2) = 0.29; p < .001). In 56.6% (n = 99) of ail measurements, the discrepancy between TEE and To-Go was >0.50 L/min /m(2). The magnitude of the discrepancies of the TEE was significantly corr elated with age (r(2) = 0.17; p = .02). Measurements were in phase in 93.2% of all arterial pulse waveform analysis and in 84.9% of all TEE readings ( p < .001). Conclusions: The arterial pulse waveform analysis exhibits a greater accura cy and reliability as compared with the TEE with regard to overall bias, nu mber of inaccurate readings, and phase lags. The arterial pulse waveform an alysis may be useful for the monitoring of hemodynamic changes. However, bo th methods fail to be a substitute for the TD-GO because of a substantial p ercentage of inaccurate readings.