The standard technique for determining cardiac output is the indicator dilution method developed by Hamilton. One end of a small catheter is inserted into the radial artery and the other end is connected to a densitometer, which can automatically record the concentration of the dye in the blood. A known amount of dye, 5.6 mg, is injected rapidly, and the following data is obtained:

Plotting the above data results in the dye dilution curve in Figure. The concentration reaches a maximum value at about 15 seconds and then falls off, followed by a rise due to the recirculation of dye. The curve is replotted on a semilog graph in Figure. Notice that a straight line approximates the descending limb of the

dilution curve. In order to separate out the recirculation effect, analysts extend the straight-line portion. The cardiac output can then be calculated from
C = M/A x 60 s/min
Where C = cardiac output [L/min], M = amount of injected dye (mg), and A = area under the curve with the linear correction. Calculate the cardiac output of this patient using the trapezoidal rule whit a step size of 0.5s.

Time, Concentration, Concentration, Time, mg/L mg/L 21 2.3 1.1 01 23 25 0.9 0,11 0.4 1.75 2.06 27 11 29 31 4.1 13 2.25 2.32 15 33 35 17 19 2.43 4.2