NA;A macroparticulate radiographic contrast material lpar;soluble gelatin spheres with 50 to 60percnt; waterhyphen;soluble contrast mediumrpar; has proved technically applicable in accurate tracing of bloodhyphen;flow currents. Its usefulness for radiologic determination of volume flow in large vessels was evaluated on the basis of a simple technique for cardiac output determination, tested in 91 experiments with 18 dogs. The length of travel per cardiac cycle for injected contrast particles flowing through the ascending aorta was measured in highspeed cinefluorographic recordings. Multiplication of this length with pulse rate and a representative crosshyphen;sectional area of the aorta yielded cardiac output estimates ranging from one to ten liters per minute, with significant correlation to results obtained with methods based on blood pressure measurements and dyehyphen;dilution studies lpar;correlation coefficients 0.84 to 0.92 with good approximation to linear regressions between 0.84 and 1.22rpar;. Similar analysis of few observations employing the pulmonary artery gave poor correlation owing to difficulties in defining a useful cylindrical segment of that artery and to superimposition of the right atrium. The method is technically simple, is based on direct observation and permits a beathyphen;tohyphen;beat analysis lpar;standard error in three to eight consecutive cycles about 9percnt; referring to results of blood presure measurementsrpar;.
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