Measurement of Cardiac Output by Thermodilution with Constant Rate Injection of Indicator

Abstract

A mathematical formula has been suggested for measurement of cardiac output by the thermodilution technique using constant rate indicator injection. The theoretical assumptions have been checked in model experiments and in experiments on dogs. The best reproducibility was attained when the indicator was injected into the right atrium, near the tricuspid valve, and the dilution was detected in the pulmonary artery. Recirculation of the cool indicator is negligible and takes place only after the attainment of the curve plateau. No systematic difference was found in simultaneous measurements made by the Fick principle and the injection technique. The correlation coefficient, r , was 0.96.