Effect of ventilation with different gas mixtures on experimental lung air embolism.

Abstract In six anesthetized, curarized and mechanically ventilated dogs, air was infused via a jugular vein at 0.1 cm 3 /kg/min for 25 min. This induced a progressive increase in pulmonary artery pressure (Pap) while arterial P O 2 (Pa O 2 ) and end tidal P CO 2 (P ET CO 2 ) decreased. Systemic arterial pressure, dynamic lung compliance and total pulmonary resistances were not affected. Changes tended to plateau by 20 min with a peak increase in Pap of 80 ± 13% and decrease in Pa O 2 and P ET CO 2 of 22.2 ± 2.8% and 14.5 ± 2.1% respectively. When embolization was stopped these values returned to control levels within 30 min. During air infusion (at 20 min) some dogs were switched from ventilation with air to ventilation with the following gas mixtures: SF 6 80%O 2 20%, He80%O 2 20%, N 2 O80%O 2 20%. During the final 5 min of air infusion, He and, to a greater extent, N 2 O breathing results in an immediate and marked further increase in Pap and decrease in Pa O 2 and P ET CO 2 . In contrast SF 6 produced rapid improvement in these parameters with return to near control levels. The recovery time after stopping infusion was greatly shortened with SF 6 but was unaffected by He of N 2 O. These results are explained by different rates of gas transfer between the intravascular bubbles and the various alveolar gases. These findings show that ventilation with SF 6 results in marked improvement in the gas exchange abnormalities produced by air embolism.