Accuracy of a non-invasive monitor of oxygen delivery in patients undergoing cardiac surgery

Monitoring heart function is routinely undertaken during cardiac surgery by inserting a plastic tube (pulmonary artery catheter) into a blood vessel into the neck and then advancing the plastic tube into the heart This technique can on occasion injury the heart or lungs. We have developed a novel monitor that may provide the same monitoring of heart function but without the need to insert a plastic tube into the heart (non-invasive) and therefore remove the risk or injury to the heart and lungs. We would like to assess the accuracy of this new non invasive monitor in comparison to the routine invasive method. The technique uses two distinct wavelengths of light in the infra-red range. The study will be undertaken in patients undergoing cardiac surgery. In addition to the routine invasive monitoring you will also receive non-invasive monitoring of heart function. A sensor will be placed on the skin over the heart. The sensor emits light into the heart and this provides a signal that assesses the adequacy of heart function. An ultrasound machine will be used to optimally position the sensor over the heart (these are the machines used in pregnant women to gain images of the baby). The monitoring of the heart function will continue until the patient is stable and discharged from the Intensive Care Unit. The results of the non-invasive monitor will be compared with those obtained using the routine invasive method. All patients will have invasive and non invasive monitoring. The accuracy of the non-invasive method will be compared with the invasive pulmonary artery catheter in each patient.