2.1 The CardioQ-ODM (Deltex Medical) is an oesophageal doppler monitor that assesses cardiac output and intravascular fluid status.
2.2 Oesophageal doppler monitoring is undertaken with a single-use probe, which is placed in the oesophagus via the mouth or nose. The device generates a low-frequency ultrasound signal, which is reflected by red blood cells travelling down the aorta. By applying the doppler principle, the reflected signal can be used to determine flow velocity. A validated nomogram is used to derive volumetric data such as stoke volume and cardiac output. Fluid management during surgery is guided by the use of the CardioQ-ODM to monitor changes in stroke volume following repeated fluid challenges. This approach can correct functional hypovolaemia, which is often present before surgery, and can optimise intravascular volume.
2.3 The cost of the CardioQ-ODM is approximately £11,000. The cost of probes varies depending on the intended length of use. The average cost of a probe is approximately £67 for patients undergoing surgery and approximately £118 for patients in the critical care unit. The cost of the CardioQ-ODM and probes may vary because of differences in purchasing contracts.
2.4 Optimising intravascular volume and cardiac output is essential to ensure adequate organ perfusion in patients who are undergoing major surgery or who are critically ill.
2.5 Cardiac output is monitored using a variety of techniques, such as inserting a pulmonary artery catheter or using systems based on pulse contour analysis and dye dilution. Less invasive methods include trans-oesophageal echocardiography and measuring thoracic electrical bioimpedance. These techniques are combined with conventional clinical assessment. In some cases a central venous catheter is inserted to measure cardiac pre-load.