Cardiac output measurement graphs

A marker substance is injected into a central vein. A peripheral arterial line is used to measure the amount of the substance in the arterial system. A graph of concentration versus time is produced and patented algorithms based on the Stewart-Hamilton equation (below) are used to calculate the cardiac output. 

Much of the criticism of the interpretation of Starling s original measured input-output relations was resolved by the introduction of a family of cardiac function curves [74], which accommodated neural and metabolic stimulation of the heart. Such influences manifest themselves in graphs of input (preload)-output (stroke volume, stroke work, etc.) as counter clockwise rotation (steeper) and stretch along the output (vertical) axis. Alteration in parameter c in Equation 18.1 and Equation 18.2 carries major responsibility for these modifications. In addition, it has recently been found that the cardiac function curve can be shifted along the horizontal (preload) axis [75]. This shift is effected by changes in air pressure, pe, external to the cardiac chambers, such as caused by the respiratory system, or by CPR, and modifies Equation 18.2 by approximation to... 

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