European heart journal
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European heart journal · Dec 1990
ReviewDoppler ultrasonic measurement of cardiac output: reproducibility and validation.
The Doppler ultrasonic estimation of cardiac output in man is reviewed. Minimal requirements for accurate measurements are discussed, and the published results of reproducibility studies and validation studies are summarized and analysed. Analysis of Doppler records has a coefficient of repeat determination of 5-8% for aortic or LV outflow tract measurements and this is higher for other sites. ⋯ Thus a single measurement may vary up to +/- 28% over time with no true change in cardiac output. For cardiac output determination, the Doppler methods show accuracies varying from 10 to 22% (coefficient of variation of the differences between methods) indicating that a single aortic based measurement only reliably lies within +/- 28% compared with other 'standard' methods, and during exercise the accuracy is less (+/- 44%). Doppler methods are safe, fairly reproducible and reasonably accurate methods for measuring cardiac output in selected patients provided signal quality is adequate during recording.
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European heart journal · Dec 1990
Continuous cardiac output monitoring by pulse contour during cardiac surgery.
Most pulse contour methods are unreliable under changing haemodynamic conditions, because no corrections are made for pressure-dependent compliance and reflections of pressure waves. The pulse contour method of Wesseling includes such corrections. Four thermodilution measurements equally spread over the ventilatory cycle were used to calibrate and evaluate this pulse contour method. ⋯ COth, (r = 0.94). The standard deviation for the difference between the methods against the mean of the methods was 10.6%. We concluded that the corrected pulse contour method estimates cardiac output accurately, even when heart rate, blood pressure, and total peripheral resistance change substantially.
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Cardiac output estimation is an important and much needed measurement for assessing patients in heart failure. In hypertension, it is vital for understanding the haemodynamic basis of the disease and the mode of action of drugs. Measurements of blood pressure and cardiac output provide the only means of estimating peripheral resistance. ⋯ Doppler velocimetry is the most promising technique, but it requires complex computer analysis and, as yet, can reliably be used only to measure changes in cardiac output in an individual. The technique has been assessed against the electromagnetic flowmeter in man and gives reasonable accuracy and repeatability. Echocardiography and impedance cardiography are not yet satisfactory for clinical use; neither are the radionuclide methods, apart from the 'first pass' method, but this also needs further verification.