ObjectiveTo evaluate the reproducibility and accuracy of a new pulmonary artery catheter system that provides both right ventricular ejection fraction and continuous venous oxygen saturation monitoring.DesignCriterion standard study.SettingUniversity medical center.PatientsA consecutive sample often patients undergoing elective coronary artery bypass surgery provided informed consent for the study. Exclusion criteria included emergency surgery or clinically important preoperative tricuspid regurgitation as assessed by echocardiography. None of the patient sample was excluded.MeasurementsCatheter-derived mixed venous and arterial oximetry data were compared with simultaneous values obtained using conventional laboratory cooximetry methods. Measurements were performed before cardiopulmonary bypass and intermittently up to 48 hrs after cardiopulmonary bypass. The variability of cardiac output and computed right ventricular ejection fraction was also assessed concurrently with the oximetry analysis.ResultsA significant correlation was observed for mixed venous oxygen saturation between catheter-derived and laboratory cooximetry data (r2= .81,p<.01). Similarly, arterial oxygen saturation values obtained from pulse oximetry and laboratory values were significantly related (r2= .81,p< .01). The coefficient of variation for each set of five repeated measurements for cardiac output was 8%, and for computed right ventricular ejection fraction, it was 16%.ConclusionsThe combined catheter system provides the means to monitor both mixed venous oxygen saturation and right ventricular ejection fraction. These data provide a reliable and detailed assessment of cardiopulmonary function that should prove beneficial in the critical care setting. (Crit Care Med 1992; 20:1650–1656)