Loss of diffusible indicator in the pulmonary vascular circuit

In this study, the loss of a diffusible indicator in the pulmonary vascular circuit was quantitated by comparing cardiac output values obtained by measuring paired dilution curves, one from the pulmonary artery (PA) and the other from the aorta, resulting from the injection of a few ml of 5% saline in the right atrium. Cardiac outputs were calculated from the PA and aortic dilution curves from the same indicator injection in 10 anesthetized dogs. From 43 paired trials, the cardiac output values derived from the aortic dilution curves exceeded those obtained from the PA, indicating loss of this diffusible indicator in the pulmonary vascular circuit.