A comparative study of cardiac output in neonates supported by mechanical ventilation: measurement with thoracic electrical bioimpedance and pulsed Doppler ultrasound.

In newborn infants supported by mechanical ventilation, cardiac output was measured simultaneously with thoracic electrical bioimpedance and pulsed Doppler ultrasound to determine whether the impedance technique is reliable and accurate in this age group. The mean difference between paired measurements with the two techniques in 26 subjects was negligible (less than 1 ml/kg/min), with 95% confidence limits being approximately 11% of the mean Doppler-derived cardiac output. In addition, the two techniques related well (correlation coefficient r = 0.94) over a wide range of Doppler-derived cardiac output measurements (120 to 530 ml/kg/min). In 8 of the 26 subjects, cardiac output was observed for 7 to 12 hours. The mean difference between the Doppler and impedance techniques was 6.1% to -0.7% of the Doppler value. Thoracic electrical bioimpedance is applicable to newborn infants and offers a continuous noninvasive method of cardiac output measurement.