Correction of Distortion in Dye Dilution Curves due to Sampling Systems

Abstract

AUTHORS' SYNOPSIS. The degree of distortion in dye curves due to sampling and recording systems was estimated and appropriate correction factors were determined. These factors were used in recording corrected dye curves in circulatory models and during left heart catheterization. Calculations of ventricular ejection fractions and volumes were made .from the corrected curves. The ideal indicator dilution curve is one which measures the instantaneous time-concentration relationship of the indicator substance without distortion. In order to obtain such distortion-free curves, it has been necessary to utilize a detector for the indicator which can be placed in an intravascular site. Various techniques utilizing thermodilution, saline conductivity, polarographic or fibre-optics determinations have been introduced. Each of these is limited to a large degree by shortcomings of calibration, stability, or price. Dye dilution curves are widely used and are readily calibrated. However, withdrawing blood from the body through a cuvette densitometer necessarily introduces distortion into the curve, which is not present with the other, intravascular recording techniques. The degree of distortion is dependent upon the nature of the sampling and measuring systems. Various investigators have described the effect on dilution curves obtained by using different lengths and diameters of tubing for connection of the