[abstract] PHARMACOLOGICAL MODIFICATION OF INERT GAS ELIMINATION.

Abstract

Inert gas uptake and elimination are important for the etiology of decompression sickness and these processes are highly dependent on blood circulation. Hence, we investigated ways to modify circulation, and thus the rate of gas exchange within the idea of eventually influencing the morbidity of decompression sickness. This (ongoing) study addresses the effects of several drugs expected to increase tissue blood flow on N2 elimination during inhalation of a 21% O2 in Ar mixture for 2 hrs. The results are from triplicate double-blind measurements in 4 subjects. One hr before the start of the N2 washout the subjects ingested either a placebo, 2.5 mg of terbutaline sulfate, 10 mg of isoproterenol hydrochloride or 300 mg of papaverine hydrochloride. Nitrogen elimination was measured in expired gas, collected in 10 min aliquotes which were analyzed for volume and composition (gas chromatography). Cardiac output (impedance cardiography) was also recorded. Relative to placebo conditions, papaverine showed slight, nonsignificant reductions in both cardiac output and nitrogen yield; terbutaline offered a mixed picture, with varying increases in cardiac output (up to 164% of control in one subject) but no significant increase in group mean or in N2 yields; isopreterenol showed an insignificant increase in group-mean cardiac output by 8% of control at 55 min and by 5% at 125 rnin while the N2 yield was raised by 17% (p < 0.05) at 55 min and 10% (p < 0.01) at 125 min. The effects with the latter two drugs suggest further experiments should be performed with improved dosage and timing relative to the washout schedule. Supported by New York Sea Grant Institute, NA90AADSG078.