Ductus venosus flow velocity in newborn lambs during increased pulmonary artery pressure

The aim of the present study was to assess with ultrasound the ductus venos us flow velocity in newborn lambs with increasing pulmonary artery pressure s and to evaluate whether this is a useful method to detect elevated pulmon ary artery pressure. The ductus venosus flow velocity was studied with puls ed-wave Doppler echocardiography in nine newborn lambs less than or equal t o 30 h old. The lambs were anesthetized, mechanically ventilated, and instr umented to measure mean airway pressure and pulmonary artery and arterial b lood pressures. A vascular occluder was placed around the main pulmonary ar tery. With mean pressures ranging from 20 to 50 mm Hg in the pulmonary arte ry, the ductus venosus flow velocity was examined. In seven lambs, the mean portal pressure and central venous pressure were also measured, With a ste pwise increase in the pulmonary artery pressure, the minimum ductus venosus flow velocity during atrial systole decreased to a reversed how, and the d uration of this reversed flow component increased. The systolic forward pea k flow velocity signal also gradually decreased. No changes were detected i n the mean central venous or in the portal pressure with increasing pulmona ry artery pressure or changes in ductus venosus flow. The how velocity in t he ductus venosus, which is higher than in other precordial veins, shows a reduction and even reversal of the nadir and an increase of the duration of reversed flow during atrial systole as a response to increased pulmonary a rtery pressure. Thus, Doppler ultrasound of the ductus venosus flow velocit y may be a useful noninvasive diagnostic supplement to detect pulmonary hyp ertension of the newborn.