Clinical evaluation of the edwards laboratories and oximetrix mixed venous oxygen saturation catheters

Mixed venous oxygen saturation is continuously monitored during and following cardiac operations in many institutions. Important therapeutic decisions may depend on the values indicated by the instrument. The accuracy of the system used is therefore of critical importance. Twenty-seven patients scheduled for coronary artery bypass surgery were monitored with either an American Edwards Laboratories (Irvine, CA) or Oximetrix, Inc (Mountain View, CA) fiberoptic pulmonary artery catheter. After preinsertion calibration, the values measured by the instruments were compared to blood samples analyzed with an Instrumentation Laboratories IL 282 cooximeter at eight intervals. It was found that under these clinical conditions there was significantly less difference in the values measured with the Oximetrix catheter v those determined with the IL 282 co-oximeter as compared with the values measured with the American Edwards catheter v the IL 282 co-oximeter. The percentage difference in oxygen saturation (ie, error) measured with the Edwards Laboratories catheter increased over time, averaging more than 7.5% at the last three data points.