Measurement of cardiac output with a non-invasive continuous wave Doppler device versus the pulmonary artery catheter: a comparative study
ABSTRACT
Introduction and aim: Cardiac index remains an importantmeasured variable used to optimise fluid and haemodynamicsupport in the postoperative cardiac setting. Recentdevelopments in non-invasive continuous wave Dopplerdevices enable rapid assessment of cardiac index withdecreased morbidity. This study aimed to determine theclinical utility of one such device, the USCOM device (USCOMLtd, Sydney, NSW), in assessing cardiac index compared withinvasive continuous measurements of cardiac index using apulmonary artery (PA) catheter.
Methods: A prospective study was undertaken in patientsadmitted to an intensive care unit after cardiacrevascularisation, open-heart surgery or cardiac or pulmonarytransplant, most of whom required haemodynamic support.Cardiac index was measured by a single operator using theUSCOM device. Continuous cardiac index measurementsusing the PA catheter were obtained (blinded to USCOMmeasurements) within 15 minutes of the USCOMmeasurement.
Results: 30 patients were enrolled. Adequate Doppler signalswere obtained in 26, yielding 34 paired measurements.Comparison of the two methods using a Bland-Altmananalysis identified a bias of 0.22 with limits of agreement of- 1.17 (- 1.53 to - 0.82) and 1.62 (1.26 to 1.97), representinglimits of agreement for interchangeability of ±52%.
Conclusion: In a heterogeneous population ofpostoperative cardiac patients, non-invasive determination ofcardiac index using USCOM had limited clinical utility.Doppler flow signal quality may have been affected byintrathoracic air, patient position and operator learning curve.Given accepted inherent inaccuracies of continuous cardiacoutput assessment, further investigation is required tovalidate the suitability of USCOM in this patient population.
Crit Care Resusc 2006; 8: 309-314
