A Comparison of Cardiac Output by Thoracic Impedance and Direct Fick in Children With Congenital Heart Disease Undergoing Diagnostic Cardiac Catheterization

Objective(s)To evaluate the measurement of cardiac output (CO) using continuous electrical bioimpedance cardiography (Physioflow; Neumedx, Philadelphia, PA) (COPF) with a simultaneous direct Fick measurement (COFICK) in children with congenital heart disease.DesignA prospective cohort study comparing 2 methods of measurement of CO.SettingA quaternary university-affiliated pediatric hospital.ParticipantsChildren undergoing cardiac catheterization for clinical care.InterventionsThe Physioflow measured continuous real time CO in 15-second epochs and simultaneous measurement of cardiac output by direct Fick (with mass spectrometry to assess VO2) were acquired.Measurements and Main ResultsSixty-five patients were recruited, and data from 56 (25 males) were adequate for analysis. The median age at study was 3.5 years (range, 0.4-16.6 years), and the median body surface area was 0.62 m2 (range, 0.31-1.71). There were 25 of 56 (45%) with univentricular physiology. A total of 19,228 Physioflow data points were available for the analysis of which 14,569 (76%) were valid; 96% of the invalid measurements were identified as artifacts by the device. The average cardiac index of valid measurements was 3.09 ± 0.72 L/min/m2. Compared with the Fick CO, the mean bias was −0.09 L/min, but the 95% limits of agreement were −3.20 to +3.01 L/min/m2. Consequently, only 20 of 56 (36%) of measurements were within 20%, and 31 of 56 (55%) of measurements were within 30% of each other.ConclusionsCompared with measurements made by direct Fick, CO measured using the Physioflow device was unreliable in anesthetized children with congenital heart disease.