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

Intermittent recordings of Doppler flow velocity and cardiac output are of value during intensive care of the sick newborn infant but result in repeat ed disturbance of the child. We describe a new device for making continuous precordial recordings of Doppler flow velocity from the pulmonary artery i n healthy resting newborn infants. Optimal probe siting was evaluated in si x babies, and signals were found to be best when the pulmonary artery was i nsonated from the mid left parasternum. Continuous recordings were made in 13 other babies. Pulmonary artery velocities and, by calculation, cardiac o utput were measured continuously over periods ranging from 24 to 60 min. Me dian 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 si multaneous display of signal power allowed independent assessment of artifa ctual 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 variabilit y in right ventricular output.