Development of a system to record cardiac output continuously in the newborn

Abstract

Intermittent recordings of Doppler flow velocity and cardiac output are of value during intensive care of the sick newborn infant but result in repeated disturbance of the child. We describe a new device for making continuous precordial recordings of Doppler flow velocity from the pulmonary artery in healthy resting newborn infants. Optimal probe siting was evaluated in six babies, and signals were found to be best when the pulmonary artery was insonated from the mid left parasternum. Continuous recordings were made in 13 other babies. Pulmonary artery velocities and, by calculation, cardiac output were measured continuously over periods ranging from 24 to 60 min. Median right ventricular output ranged widely from 148 to 246 mL·kg-1·min-1. In contrast, for individual babies, the values were remarkably stable: the interquartile ranges varied from 13.2 to 29.9 mL·kg-1·min-1. The simultaneous display of signal power allowed independent assessment of artifactual changes in cardiac output. This technique is feasible in healthy term infants and now requires evaluation in the intensive care setting where it may provide useful information concerning trends and short- term variability in right ventricular output.