Revised Equations for Calculation of Blood Flow and Central Blood Volume From Indicator-Dilution Curves

¹ From the Section of Physiology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota

A revised equation for the calculation of blood flow from indicator-dilution curves is presented that utilizes different parameters of the curve. This relationship clarifies the basis for several of the simplified empirical equations for calculation of blood flow and suggests an expanded usefulness in their application to abnormal dilution curves. The concept of a mean passage time is introduced and its similarity to the mean transit time is demonstrated by comparison of the values obtained for these two parameters determined from 9I dilution curves recorded from healthy persons and from patients with stenotic valvular cardiac disease. An equation is given for the portion of the Stewart-Hamilton central blood volume associated with the curve proper. This volume is equal to the quotient of the quantity of indicator injected and the peak concentration of the resulting dilution curve and is a measure of the degree of dispersion of the dye-blood mixture during its first traversal of the vascular system. It is of considerable academic and practical interest that it can be calculated without knowledge of the cardiac output and without need for replotting the indicator-dilution curve.