Changes in the pattern of regional pulmonary blood flow after PGF2α infusion in pregnant women

The central haemodynamics and regional lung function were measured in the sitting position before and after infusion of prostaglandin F2α (PGF2α) in seven healthy women in the first trimester of pregnancy. The dosage level of PGF2α was: 100 μg/min for 10 minutes followed by 300 (μg/min for 5 minutes. The pulmonary arterial pressure, wedge pressure, and cardiac output were measured by means of a flow directed Swan-Ganz catheter introduced through an antecubital vein. The regional perfusion of the lungs was determined, in the sitting position, by external counting over the chest following intravenous injection of Xe133. The thoracic impedance was measured with the Minnesota Impedance Cardiograph Model 304A and the impedance was considered as an expression of the thoracic fluid volume. A significant redistribution of the pulmonary blood flow after PGF2α administration was found, ie an increase in the apical blood flow and a reduction in the basal blood flow. Further, the point of maximal blood flow moved in direction of the apex. A significant increase in both arterial [1.92·2.76 kPa (14.4·20.7 mmHg)] and wedge pressures [0.56·0.83 kPa (4.2·6.2 mmHg)] was found at the highest dosage level, whereas no changes were seen in the cardiac output and thoracic impedance. The findings indicate vasoconstriction of the arterial and possibly on the venous side of the pulmonary vascular bed during PGF2α infusion.