RELATIONSHIP BETWEEN VENOUS BUBBLES AND HEMODYNAMIC-RESPONSES AFTER DECOMPRESSION IN PIGS

We present a new pig model for studying relationships between venous g as bubbles and physiologic effects during and after decompression. Six teen pigs were anesthetized to allow spontaneous breathing. Eight of t hem underwent a 30-min exposure to 5 bar (500 kPa) followed by a rapid decompression to 1 bar (2 bar/min); the remaining eight served as con trols. The pigs were monitored for intravascular bubbles using a trans esophageal echocardiographic transducer, and bubble count in the two-d imensional ultrasound image of the pulmonary artery was used as a meas ure of the number of venous gas bubbles. Effects on physiologic variab les of the pulmonary and the systemic circulations were either measure d or estimated. We detected venous bubbles in all pigs after decompres sion, but the interindividual variation was large. The time course of changes in the mean pulmonary artery pressure, in the pulmonary vascul ar resistance, in the arterial oxygen tension, and in the pulmonary sh unt fraction followed the time course of the bubble count. In contrast , such a relationship to the number of venous gas bubbles was not foun d for the immediate increase in mean arterial pressure and for the cha nges in the other variables of the systemic circulation. We conclude t hat the number of venous gas bubbles, as evaluated by the bubble count in the ultrasound image of the pulmonary artery, is clearly related t o changes in the variables of the pulmonary circulation in this pig mo del.