Effect of patent ductus arteriosus on water accumulation and protein permeability in the lungs of mechanically ventilated premature lambs.

To examine the effect of a patent ductus arteriosus on water accumulation and protein permeability in the premature, ventilated lung, we studied 16 lambs at 121-127 d gestation (term = 145 d). Water accumulation was assessed by the wet:dry wt ratio of the blood-free left lung. Protein permeability was assessed by the albumin content and by the recovery of 125I-albumin in the right lung lavage fluid 1 h after intravenous injection. Using a model that allows mechanical control of ductus patency, we compared nine lambs with patent ductus (left-to-right shunts 42 +/- 18% to left ventricular output) with seven lambs with closed ductus. The animals were studied over 3 h. In the open ductus lambs, 0.85 +/- 0.36 and 1.76 +/- 1.87%/h of the injected 125I-albumin was recovered in the lavage fluid and lung tissue, respectively. In the closed ductus lambs, the corresponding amounts were 0.71 +/- 0.21 and 0.71 +/- 0.22%/h; these differences were not statistically significant. Similarly, blood-free wet:dry ratios did not differ significantly between the two groups (7.01 +/- 1.28 open ductus versus 6.55 +/- 0.82 closed ductus). We concluded that patency of the ductus arteriosus does not significantly affect water accumulation and net protein transudation into the airways of preterm lambs in the first hours of life. Therefore, some other feature of immaturity must be responsible for the large protein leaks previously observed by others.