Testing the response of a cardiac output meter using an artificial circulatory system

The variation in the response of a cardiac output flowmeter to several variables was investigated. An artificial circulatory system was constructed to give independent control of the variables. It was found that variations in the earlobe density, the amount of dye injected and the hematocrit value have little influence on the recorded flow which does, however, depend on the shape of the dilution curve. The values given by the instrument are too low for broad curves and too high for sharp ones, with an error of up to 25%.