Competitive pulmonary flow in infancy: The effect of respiration

Superior caval flow during positive pressure mechanical ventilation and spo ntaneous breathing was investigated by Doppler echocardiography in a neonat e with a coexisting superior cavopulmonary shunt and an aortopulmonary shun t. During positive pressure ventilation, retrograde systolic flow in the su perior vena cava was recorded, with low velocity anterograde flow. This pat tern was reversed during spontaneous respiration. Low intrathoracic pressur e plays an important role in maintaining anterograde pulmonary blood Bow in patients with this physiology. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.