Shunts in patients with respiratory distress syndrome

To the Editor.— Although I agree with many of the echocardiographic findings of Walther et al1 they have not given us sufficient data to draw their main conclusion: that large right-to-left (R-L) shunts are common in preterm neonates with severe respiratory distress syndrome (RDS). They base this conclusion on two observations. First, they believe that aortopulmonary pressure differences are small in these neonates. Pulmonary arterial pressures in RDS are high2 but, as previously published data have shown,3 they are predominantly subsystemic and therefore not likely to be conducive to a large R-L shunt.