COMPARISON OF HEMODYNAMIC-EFFECTS DURING VENOUS AIR INFUSION AND AFTER DECOMPRESSION IN PIGS

We have compared haemodynamic effects of venous gas emboli during cont inuous air infusion into the right atrium and after rapid decompressio n in pigs. Eight anaesthetized and spontaneously breathing pigs receiv ed continuous air infusion at a rate of either 0.05 ml.kg(-1).min(-1) (six pigs, air infusion group) or 0.10 ml.kg(-1).min(-1) (two pigs). A nother eight pigs (decompression group) underwent a 30-min compression to 5 bar (500 kPa, absolute pressure), followed by a rapid decompress ion (2 bar.min(-1)). Haemodynamic variables were measured or calculate d, and bubbles in the pulmonary artery were monitored using transoesop hageal echocardiography. The results showed less variation in the maxi mal increase in mean pulmonary arterial pressure (<(BP)over bar>(a,pul m)) during air infusion (0.05 ml.kg(-1).min(-1)) than after decompress ion, although the mean maximal increase did not differ between the two groups [28.0 mmHg (3.73 kPa), 95% confidence interval (CI) 23.5-32.5, vs 32.0 mmHg (4.27 kPa), 95% CI 25.3-38.7, P = 0.3]. The <(BP)over ba r>(a,pulm) stabilized or decreased very slowly after peak values were reached in the air infusion group, whereas the <(BP)over bar>(a,pulm) decreased rapidly during the same period in the decompression group. N o significant changes in mean arterial pressure were observed during a ir infusion (0.05 ml.kg(-1).min(-1)), in contrast to the rapid increas e and the subsequent decrease, that appeared after decompression. Fina lly, the maximal bubble count was much lower in the air infusion group than in most of the pigs in the decompression group. The two pigs tha t received 0.10 ml.kg(-1).min(-1) stopped breathing after 5-min infusi on, developed arterial hypotension and died.