Comparison of bioimpedance and Doppler ultrasound cardiac output in CAPD patients

The reproducibility and reliability of cardiac output (CO) measurement by transthoracic electrical bioimpedance (TEB) and dual beam Doppler ultrasound methods were compared in 9 uremic patients during treatment with continuous ambulatory peritoneal dialysis (CAPD). CO was measured simultaneously by each method during supine rest and 70 degree passive head-up tilt on two separate days. The effect on CO after the infusion of dialysate was also studied on day 1. CO, stroke volume (SV) and heart rate (HR) measurements were reproducible by each method. The median day to day differences (95% confidence intervals) in CO and SV were 0.6 (-0.3, 1.8) l/min and 10 (-1.5, 24.5) ml for TEB and 0.7 (-0.5, 2.2) l/min and 13 (-1.0, 30.5) ml for Doppler at supine rest; 0.4 (-0.2, 0.9) l/min and 11 (-0.5, 19.0) ml for TEB and 0.5 (-0.3, 1.2) l/min and 8 (-5.0, 16.0) ml for Doppler during tilt (p > 0.05 in each case). Data were unobtainable by TEB at five time points while none were lost by Doppler. This is due to incorrect HR or poor quality signals detected by TEB. CO and SV measured by Doppler were higher than that by TEB during supine rest (p < or = 0.01) but not during passive tilt. As a result, there was significant change (p < or = 0.01) in CO and SV from supine to tilt measured by Doppler but not by TEB. Neither TEB nor Doppler detected significant change (p > 0.05) in CO or SV after the infusion of dialysate, in either the supine or tilt positions.(ABSTRACT TRUNCATED AT 250 WORDS)