Experimental Pulmonary Embolism

Autologous blood clot was used to produce pulmonary macroembolism, and lycopodium spores to produce microembolism in normal mongrel dogs. Pressures were recorded from the pulmonary artery, left atrium and femoral artery; cardiac output and pulmonary blood volume (PBV) were determined using sequential indicator dilution curves from injections into the pulmonary artery and left atrium. Macro- and microembolism caused comparable elevations of pulmonary artery pressure and total pulmonary resistance. Macroembolism with blood clots resulted in marked decreases in PBV and pulmonary vascular compliance. However, microembolism with lycopodium spores caused only small decreases in PBV despite a large reduction in pulmonary vascular compliance. Prostaglandin E1 infusion after microembolism had no effect on pulmonary hemodynamics, but caused significant systemic hypotension. After macroembolism PGE1 infusion decreased PBV and decreased systemic arterial pressure.