OBJECTIVE: The purpose of this study was to evaluate three modified, fiberoptic, oxygen saturation catheters as monitors of jugular venous oxygen saturation (SjvO2). METHODS: Three modified fiberoptic catheters, designated Catheters 1, 2, and 3, were evaluated. After preinsertion calibration, the catheters were inserted in the dominant jugular vein of patients with severe head injuries. The catheter reading for SjvO2 was compared with the SjvO2 value measured in a blood sample drawn through the catheter, at intervals up to 72 hours. RESULTS: Catheter 3 (a modified version of the pediatric Swan-Ganz catheter) showed significantly better performance than the other two catheters. Both the initial calibration of the catheter and the calibration with time were significantly better for Catheter 3 than for the other two catheters tested. The Catheter 3 value for SjvO2 was more than 4% different from the co-oximeter value in only 6% of the 4-hour calibration checks, compared with 26% and 29% for Catheters 1 and 2, respectively. CONCLUSION: Catheter 3, which is now being marketed as the Opticath P540-H catheter, represents a significant improvement in performance and may make SjvO2 monitoring in the intensive care unit more practical.