Measurement of Cardiac Output by Dye Dilution Technique: Use of an “Integrated” Sample Collection in Calibration of the Photometric Instrument

Abstract

Cardiac output was measured by injecting Evans blue dye into an antecubital vein and recording the brachial arterial dilution curve from a polyethylene conduit traversing the light beam of a photoelectric densimeter. A single blood sample was collected over the major portion of the primary dye curve and plasma analyzed spectrophotometrically. Optical density of this "integrated" sample expressed as a ratio against mean height of inscribed curve over the same interval gave a calibration factor for calculation of cardiac output by the Stewart-Hamilton equation. Comparison of duplicate curves showed this method more reproducible than calibration by the conventional sample drawn at the tail of the curve.