MULTICENTER TRIAL OF A NEW THORACIC ELECTRICAL BIOIMPEDANCE DEVICE FOR CARDIAC-OUTPUT ESTIMATION

Objective. To evaluate the capacity of a new thoracic electric bioimpe dance system to estimate cardiac output compared with the conventional thermodilution method. Design: Prospective, multicenter study. Settin g: A university-run county hospital, a university-run U.S. Veterans Af fairs hospital, and a university-affiliate U.S. military hospital. Pat ients: A series of 68 critically ill patients whose conditions require d pulmonary artery catheter insertion. Measurements and Main Results: A total of 842 simultaneous pairs of cardiac output estimations by con ventional thermodilution and a new thoracic electric bioimpedance syst em that uses an improved signal processing technique based on an all-i nteger-coefficient filtering technology, using a time-frequency distri bution that provides a high signal/noise ratio were evaluated. The r v alue was .86, r(2) = .74, and p < .001 by regression analysis; the mea n difference between the two methods relative to their average value w as 16.6 +/- 12.9 (SD) %; the precision was 1.4 L/min or 0.8 L/min/m(2) ; the bias was -0.013 L/min. The mean difference between successive pa irs of thermodilution measurements was 8.6 +/- 0.6 (SD) %, which was a bout half the difference between simultaneous pairs of measurement by the two methods. The changes in impedance estimations were close to si multaneously measured changes in thermodilution estimates of cardiac o utput. Conclusions: The new bioimpedance system satisfactorily estimat ed cardiac output as measured by the thermodilution technique. The dif ference between the two estimations is more than made up for by the co ntinuous noninvasive capability of the impedance system.