GE HEALTHCARE E-PRESTN, Technical Manual

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Module Frames and Modules
4 - 2
2062973-004
Equipment safety symbols
1.2 Measurement principle
1.2.1 Cardiac output and REF
Cardiac output measurement is performed using the principle of thermodilution. During
measurement, the catheter lies in the heart, with an injection port in the right atrium (RA) and a
thermistor, which is to monitor blood temperature, in the pulmonary artery (PA). A small, known
amount of thermal indicator is injected into the RA and mixed with the blood on its way to the
PA. The catheter thermistor measures the decrease in blood temperature as the blood flows
past the thermistor in the PA.
The information is stored in the module and the cardiac output is calculated from the area
beneath the time-temperature Cardiac Output Measurement Curve, as shown in figure 2.
The area under the time-temperature curve is inversely proportional to the flow rate which
corresponds to cardiac output.
The cardiac output is calculated from the equation:
C.O.= (1.08 C
T
60 V
i
(T
B
-T
i
))/(T
B
dt + C)
where:
C.O. =
Cardiac output in liters/minute
1.08 = Factor comparing the density and specific heat of 5% dextrose solution in water to
those of blood
C
T
= Correction factor for the injectate temperature rise as it passes through the
catheter and its dead space
60 = Seconds/minute
V
i
= Injectate volume in liters
T
B
= Baseline blood temperature (°C)
Ti = Injectate temperature
T
B
dt = Area under time-temperature curve between time o and x, where x is the
time when the curve has dropped to 30% of its peak value
C = Area beneath time-temperature curve between x and the end of the curve
This symbol on the module refers to defibrillator precautions. To ensure
protection against the effects of cardiac defibrillator discharge, always use
the recommended cables and leadwires only (see the supplemental
information manual). Using other cables or leadwires may result in damage
to the equipment and compromise patient and/or user safety.