Dinesh G. Haryadi

Evaluation of a thoracic bioimpedance cardiac output monitor during cardiac catheterization.

Objective: To evaluate the accuracy and precision of an advanced thoracic bioimpedance cardiac output monitor by comparing it with conventional thermodilution. Design: Prospective data collected from 47 patients undergoing routine cardiac catheterization. The new bioimpedance system differs from its predecessors in electrode system configuration, advanced signal processing, use of a modified Kubicek equation, and a reliable estimate of left ventricular ejection time from the time derivative bioimpedance signals. Setting: A cardiac catheterization laboratory in a university affiliated teaching hospital. Patients: A series of 47 relatively homogenous patients undergoing routine cardiac catheterization for suspected cardiac disease. Measurements and Main Results: The data from the first 20 patients was used to determine optimal values for coefficients in the bioimpedance cardiac output equations. The coefficients found were used when the system was tested in the subsequent 27 patients. For the last 27 patients, a total of 80 simultaneous pairs of cardiac output measurements were made by conventional thermodilution and by thoracic bioimpedance. The mean difference between the two methods was −0.31 L/min and the standard deviation of the differences was (0.76 L/min). The correlation coefficient was r2 = .72 (p < .001). Conclusions: The correlation between conventional thermodilution and thoracic bioimpedance cardiac output estimates was good and the standard deviation of the differences was lower than that reported for commercially available devices. The system can be used in the cardiac catheterization lab for reliable and continuous noninvasive measurement of cardiac output.

Evaluation of a New Advanced Thoracic Bioimpedance Device for Estimation of Cardiac Output

Objective. This study is an evaluation of a new thoracic bioimpedance cardiac output monitoring system which incorporates a modified form of the Kubicek equation and a method of estimating the left ventricular ejection time from the time derivative bioimpedance signals. Methods.The performance of the new system was compared with conventional thermodilution in a porcine model. One hundred and ninety nine (n = 199) paired measurements of thermodilution cardiac output (TDCO) (range 1.20–18.00 L/min) and thoracic bioimpedance cardiac output (BICO) were collected in 7 pigs. The bioimpedance measurements were adjusted for the animals weight and chest circumference, thus compensating for the differences in the anatomy of pigs when compared to humans. Data were compared using weighted correlation coefficient and Bland–Altman analysis. Results. The weighted correlation coefficient between TDCO and BICO values was 0.87 (n = 199). The Bland–Altman technique yielded a precision of the device of ±1.69 L/min with a bias of 0.11 L/min. Conclusion. The results from the porcine study show that the new system performed well over a wide range of cardiac outputs, comparing favorably with data from other new bioimpedance cardiac output devices currently available in the market.

Expressions of accuracy in the evaluation of cardiac output monitoring devices

evaluation study in patients undergoing cardiac surgery (155 patients, 30-85 yrs, 46-141 kg). TDco was measured using 10ml bolus of room temperature 5% dextrose. Three sequential bolus TDco measurements, phased randomly with respect to respiration, were recorded as TD1, TD2 and TD3. Regression analysis, correlation coefficients and Bland-Altman statistics were used to compare the degree of agreement between the three bolus TDco measurements. To evaluate the reproducibility of TDco, a difference of ±3 x SEM% (% standard error of mean = standard error of the mean/average CO) between two bolus TDco determinations was considered to be sufficient to be confident that they were different. 3 Bolus thermodilution cardiac output (TDco) measurements are routinely used as the gold standard when evaluating newer methods of cardiac output (CO) monitoring. The range of accuracy that is acceptable varies widely in the literature. We sought to address this issue by looking into the accuracy of TDco, since newer CO monitoring devices need to equal, if not better, the performance of the gold standard.