Regional hypoventilation and bronchoconstriction during pulmonary air embolism

The hypothesis that experimental pulmonary air embolism would lead to bronchoconstriction in the upper lungs and a shift in ventilation toward the lower lung regions was tested in anaesthetized and paralyzed dogs. During constant rate air infusion (0.15 ml X kg-1 X min-1), regional distribution indices were obtained using radioactive xenon boli injected at the mouth at residual volume. The results show that there was a shift of inspired xenon toward the dependent lungs after 30 min of air infusion and that this shift was accompanied by a rise in pulmonary artery pressure, a slight decrease in vital capacity, a significant increase in closing volume and an increase in airway resistance. Inspiring 5% CO2 after the shift did not reverse the distribution of xenon boli. Intravenous injection of isoproterenol after the changes had occurred, on the other hand, invariably returned the distribution toward control values. These findings indicate that hypoventilation and bronchoconstriction occurred in the non-dependent lungs during pulmonary air embolism.