On-line computation of cardiac output from dye dilution curves.

• Calculation of cardiac output from dye dilution curves as described by Hamilton has been well verified.' 3 The technique of calculating the cardiac output with the use of a planimeter or replotting on log paper is tedious and-often inexact. Furthermore, the necessary long delay between the dye injection and the availability of the result has limited the use of this technique in medical research. In order to circumvent these difficulties, a new technique has been developed in which a general purpose analog computer is used for automatic computation of cardiac output and the mean transit time. Removal of the recirculation hump as well as the correction for baseline offset are accomplished automatically, and the results are obtained within 20 seconds after the presentation of the dye curve to the computer. The computer circuitry and its operation are fully described and computer results compared to those obtained by the usual Stewart-Hamilton method.