The esophageal Doppler monitor in mechanically ventilated surgical patients: does it work?

Assessment of cardiac volumes and cardiac output (CO) using a pulmonary artery catheter (PAC) in mechanically ventilated patients can be inconsistent and difficult. The esophageal Doppler monitor (EDM) is emerging as a potential alternative to the PAC. This prospective study evaluated the comparative accuracy between the PAC and EDM for preload assessment and CO in mechanically ventilated surgical patients. METHODS The EDM was placed in 15 patients with PACs in place. A total of 187 simultaneously measured EDM and PAC comparative data sets were obtained. The Pearson correlation (r) was used to compare measurements, with significance defined as a value of p < 0.05.

CO measured by EDM and PAC correlated closely (r = 0.97, p < 0.0001). Corrected flow time (FTc), a measure of left ventricular filling, correlated with PAC CO to the same degree as pulmonary capillary wedge pressure (PCWP) when positive end-expiratory pressure (PEEP) was < 10 cm H2O (FTc, r = 0.51; PCWP, r = 0.56). When PEEP was > or = 10 cm H2O, FTc correlated with PAC CO better than PCWP (FTc, r = 0.85; PCWP, r = 0.29).

FTc correlates with EDM and PAC CO better than PCWP. On the basis of the current study, it is reasonable to conclude that the EDM is a valuable adjunct technology for CO and preload assessment in surgical patients on mechanical ventilation, regardless of the level of mechanical ventilatory support.