On-line computation of cardiac output with the thermodilution method, using a digital minicomputer

Abstract

In the present study, several techniques for calculating cardiac output were evaluated in order to find an accurate technique suitable for on-line digital computation. The thermodilution method was evaluated by different calculation techniques and by comparing these techniques with electromagnetic flowmeter values. Comparison of thermal dilution curves, manually calculated by the log-normal and the exponential assumption, showed a correlation coefficient of 0.978 between the two methods, the former values being 11% higher. The exponential method correlated very well with the technique, using a correction factor for injection errors (r = 0.999). Since the exponential technique correlated well with the electromagnetic values (r = 0.84) and since it was less complicated than the technique, using correction factors, this technique was chosen for automation. Comparison of exponential calculated thermodilution values with a digital computer and manually, showed a correlation coefficient of 0.991. Therefore, it was concluded that on-line computation of thermodilution curves improves the applicability of the termodilution techniques as a means of measuring cardiac output.

The effect of elevated arterial free fatty acid concentrations on hemodynamics and myocardial metabolism and blood flow during ischemia

“…The hemodynamic variables were recorded continuously on a multichannel Schwarzer recorder. Through a jugular vein a Swan-Ganz balloon guided thermistor catheter was placed in the pulmonary artery to measure cardiac output, using the thermodilution technique as previously described in detail (29). Thermodilution curves were registrated on a Linseis series 2000 recorder.…”

“…The surface under the curve was measured by planimetry. Cardiac output was calculated manually according to the log-normal assumption (29).…”

The thermodilution technique in on‐line computation of the left ventricular volumes on anaesthetized dogs

“…The thermal indicator staying in the catheter lumen after injection may dissipate through the catheter wall and cause a distortion on the latter part of the dilution curve [ 151. Therefore, if the curve did not attain the base line at the 6th beat after injection [ 19,221, it was extrapolated, to approach zero, by fitting a monoexponential function on the downslope of the curve using the least-squares procedure [23]. The area under the dilution curve (A, sec X "C) was computed by summation of the digitized curve values according to the rectangular rule.…”