Journal of Applied Physiology, Vol 71, Issue 5 1780-1786, Copyright © 1991 by American Physiological Society
Effect of aminophylline on transpulmonary passage of venous air emboli in pigs
A. Vik, B. M. Jenssen and A. O. Brubakk
Department of Biomedical Engineering, University of Trondheim, Norway.
Aminophylline has been shown to dramatically reduce the filtering capacity
of the lung in dogs during venous air embolism. Similarities have been
pointed out between the cardiovascular and respiratory systems of the pig
and of humans. We therefore wanted to find out whether aminophylline also
modifies the transpulmonary spillover of microbubbles to the arterial
circulation of the pig. Twenty-eight pigs were anesthetized with
pentobarbital sodium and mechanically ventilated. Aminophylline was
injected intravenously into 10 of the pigs before the introduction of air
bubbles into the right ventricle, while the other 18 pigs served as
controls. A transesophageal echocardiographic probe was used to detect
eventual air bubbles in the left atrium or in the aorta. Pigs received
either air infusion, at rates varying from 0.05 to 0.20 ml.kg-1.min-1, or
calibrated microbubbles, 5-300 microns diam. We found that
aminophylline-treated pigs did not show any change in spillover incidence
compared with controls. Furthermore, in both groups the spillover during
continuous air infusion seemed to be a preterminal event, because the pigs
had very low arterial pressure when arterial bubbles were observed.
Finally, there was an increase in mean pulmonary arterial pressure from 18
+/- 3.4 to 26 +/- 2.2 (SD) mmHg (n = 4, P less than 0.01) in
aminophylline-treated pigs after a bolus injection of microbubbles (less
than or equal to 50 microns, total volume less than 0.5 ml). Our results
suggest that aminophylline does not modify the transpulmonary passage of
microbubbles in this porcine model. In addition, it would seem that the
pulmonary circulation of the pig is sensitive to very small volumes of air,
when injected as microbubbles.
