Use of isoproterenol infusion to study intrapulmonary gas mixing in man.

In the present investigation, the effect of an increased cardiac output on intrapulmonary gas mixing was studied in healthy male subjects. Increase of heart rate and cardiac minute output was induced by infusion of isoproterenol, intrapulmonary gas mixing was analyzed by simultaneous washout of inert gases widely differing in molecular weight (helium and sulfur hexafluoride). Parameters, appropriate to indicate quality of gas mixing, have been crossover point (COP) and separation index (SI). During isoproterenol-induced tachycardia, the COP occurred earlier and the SI decreased. Both changes then demonstrate an improved gas intrapulmonary mixing. The movement of the heart reduces stratified inhomogeneity.