A comparison between oesophageal Doppler and continuous thermodilution for the measurement of cardiac output in critically ill patients

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Introduction

There have been concerns raised over the safety of pulmonary artery (PA) catheters. Previous studies have shown oesophageal Doppler (OD) monitoring provides a reliable, easy alternative method of assessing cardiac output (CO) in an ICU setting.

Methods

After ethical approval we studied 12 ICU patients who required PA catheters for monitoring of therapy. A continuous cardiac output (CCO) PA catheter (Vigilance monitor, Baxter) and OD probe (CardioQ monitor, Deltex), were inserted in each patient. Insertion time and complications were noted for both techniques. Measurements of CO by thermodilution and OD were recorded. Data was analysed using regression analysis and Bland-Altman for the difference between the two techniques.

Results

Twelve patients were analysed with a total of 128 pairs of cardiac output measurements. There were four complications due to PA catheters and none due to OD. Mean insertion time was 52.9 min for PA catheter and 5.8 min for OD (P < 0.0001). Thermodilution cardiac outputs were obtained between 2.9 and 15.5 L/min. Pear-son's correlation coefficient (r) for PA catheter vs OD was 0.689 (P < 0.0001). The mean difference in CO between the two methods was -0.17 L/min with limits of agreement of -4.016 to +3.676.

Discussion

To our knowledge, this is the first study to compare continuous cardiac output by thermodilution with cardiac output by OD (CardioQ monitor). OD probes are faster to insert, easier to use and safer. However, our study shows that there are major differences in the cardiac output values obtained by the two techniques.