Comparison of the effects of controlled ventilation with 100% oxygen, 50% oxygen in nitrogen, and 50% oxygen in nitrous oxide on responses to venous air embolism in pigs.

In this randomized, experimental study in 18 pigs, we have investigated the effects of inspiratory air in oxygen, 100% oxygen and 50% nitrous oxide in oxygen on the detection and consequences of venous air embolism. Each animal was tested with injections of 1.0 ml kg-1 and 2.0 ml kg-1 of air. All animals, except one in the nitrous oxide group, survived the air emboli. Systolic and diastolic arterial pressures decreased significantly in all groups after both injections of air. Pulmonary diastolic pressures increased most in the nitrous oxide group. End-tidal concentration of carbon dioxide decreased significantly in all groups after air injections. The difference in concentration of oxygen in the inspiratory and expiratory gas (O2 (I-E)) was lowest in the air group after both injections of air. On the basis of our studies we suggest that nitrous oxide should not be used during surgery associated with an increased risk of venous air embolism.