Thoracic electric bioimpedance measurement of cardiac output in the newborn infant

To evaluate thoracic electric bioimpedance as a noninvasive method for measuring cardiac output, we compared the bioimpedance measurements with those obtained by means of the thermodilution indicator cardiac output technique in seven preterm and term lambs; we also studied 17 term and preterm infants. Sixty-seven simultaneous bioimpedance and thermodilution cardiac output measurements were obtained in the animals after intravascular volme expansion (saline solution infusion) and contraction (phlebotomy). A significant correlation between the cardiac output measurements by the two methods (0.82; p<0.001) was observed. In neonates, the observed cardiac output was 198±46 ml/kg·min in the preterm infants and 178±46 ml/kg ·min in the term infants. Extrapolating animal data to the neonates, we found the thoracic segment length recommended (the average of 29% body length and electrode distance) to be accurate. These data indicate that bioimpedance cardiac output measurement (1) is comparable to measurement by the thermodilution indicator technique in the newborn animal and (2) may be suitable for use infants and children.