Respiratory effects of a patent ductus arteriosus in premature newborn lambs.
We examined the respiratory effects of a patent ductus arteriosus in 29 premature lambs (131-135 days gestational age) after infiltrating the ductal wall with formaldehyde solution (Formalin) and placing a snare around the ductus to regulate its patency. The lambs were given sheep surfactant, paralyzed, and mechanically ventilated at birth. We first compared 8 lambs with open ductus and 13 lambs with closed ductus during the 12 h after birth. Although lambs with open ductus had greater pulmonary blood flow (301 +/- 36 vs. 188 +/- 11 ml.min-1.kg-1, mean +/- SE, at 12 h of age) and mean pulmonary arterial (44 +/- 3 vs. 33 +/- 2 mmHg) and left ventricular end-diastolic (6 +/- 0.6 vs 4 +/- 0.7 mmHg) pressures, we found no differences in dynamic respiratory compliance (Cdyn = 0.55 +/- 0.07 vs. 0.55 +/- 0.03 ml.cmH2O-1.kg-1), midtidal volume resistance (62 +/- 5 X 10(-3) vs. 62 +/- 7 X 10(-3) cmH2O.ml-1.s), or functional residual capacity (FRC = 27 +/- 3 vs. 26 +/- 2 ml.kg-1). Alveolar-arterial PO2 difference was lower in the lambs with open ductus (238 +/- 65 vs. 362 +/- 37 Torr). Next, we challenged eight lambs with two separate saline infusions (50 ml.kg-1 over 3 min), each given with the ductus alternately closed or open. When the ductus was closed, FRC was unchanged, but Cdyn increased by 18% immediately after the infusion. When the ductus was open, FRC decreased by 16% and Cdyn decreased by 12%. We conclude that the premature lamb is surprisingly resistant to changes in respiratory function from ductal patency during the immediate neonatal period.
Cardiovascular Research Institute, University of California, San Francisco.
J J
JJ
Pérez Fontán
R I
RI
Clyman
F
F
Mauray
M A
MA
Heymann
C
C
Roman
D000818:Animals; D000831:Animals, Newborn / Q000601:surgery; D001784:Blood Gas Analysis; D001794:Blood Pressure; D004195:Disease Models, Animal; D004374:Ductus Arteriosus, Patent / Q000209:etiology / Q000503:physiopathology*; D005652:Functional Residual Capacity; D006801:Humans; D007231:Infant, Newborn; D008170:Lung Compliance; D012119:Respiration; D012127:Respiratory Distress Syndrome, Newborn / Q000503:physiopathology; D012756:Sheep / Q000502:physiology*; D012965:Sodium Chloride / Q000008:administration & dosage
D012965:Sodium Chloride