Effects of ductus arteriosus occlusion on pulmonary artery pressure during in utero ventilation in fetal sheep.

Abstract

Seven fetal sheep were prepared to study the short-term effects of in utero ventilation and ductus arteriosus occlusion on pulmonary artery pressure and on fetal right ventricular function assessed using the right atrial pressure-right ventricular stroke volume relationship. Nine days post-surgery (140 days gestation), blood gas and haemodynamic values were obtained before and during in utero ventilation with 100% O2, and during ventilation with the ductus arteriosus occluded. Oxygen content increased significantly from 7.2 to 14.5 ml dl-1 with ventilation and remained elevated at 14.4 ml dl-1 with ventilation with the ductus arteriosus occluded. In utero ventilation produced a left to right atrial pressure gradient and depression of the right atrial pressure-right ventricular stroke volume relationship. Ductus arteriosus occlusion during in utero ventilation reduced the left to right atrial pressure gradient, and along with a decrease in pulmonary artery pressure, resulted in an upward shift of the right atrial pressure-right ventricular stroke volume relationship, but only to the preventilation level. This study indicates that the fetal right atrial pressure-right ventricular stroke volume relationship is significantly altered, both by changes in the left to right atrial pressure gradient and by changes in pulmonary artery pressure seen with in utero ventilation and subsequent ductus arteriosus occlusion.