Venous air embolism through infusion sets. Theoretical considerations, model experiments and prevention.

Some infusion sets are so designed that, even when infusing into peripheral veins, a negative pressure may occur in a large portion of the infusion tubing, with the result that air enters the system from a side drip which has run dry, or though leaks. In model experiments, it was found that, when infusing into a peripheral vein, volumes of air up to 13 ml per min can enter the system from an empty side drip. From an analysis of the pressure conditions in infusion sets before and during infusion, it is concluded that infusions sets should be so designed that clamps and connections forthe attachment of a side drip are placed distally on the infusion tubing. Even then there is a risk of air embolism. The tubes for both the main and the side drip should therefore be so long that each of them can be fixed below the heart level of the patient, thus forming a waterlock and preventing the entry of air.