A cardiac output computer for the rapid analysis of indicator dilution curves

The determination of cardiac output and central blood volume is of considerable importance, not only in cardiac research but i the diagnosis and treatment of heart disease. At present, the most clinically adaptable method of determining these parameters is the indicator-dilution technique. However, analysis of indicator-dilution curves is laborious, requiring 20–40 min. of a skilled operator's time. A simple instrument has been devised which permits the determination of cardiac output and central blood volume in less than one min. The computer described in this paper makes use of an electronically-generated curve which is displayed on a CRT and optically superimposed on the actual indicator-dilution curve. Three manual controls, used to match the curves, yield the desired parameters. The computer may be used to analyse curves within the following ranges: Curve amplitude (2A)—2.5–10 cm; Period (T)—2.5–10 sec; Time constant (CT)—(0.25–1)×T sec; Injection (I)—5–12.5 mgm; Calibration (M)—5–1.2 cm/mgm-liter; Cardiac output—0–48 liters/min Mean transit time—25 sec full scale.