In vivo assessment of catheter-tip PO2 sensor: sampling lumen fabrication

Fabrication of the sampling lumen of an intra-arterial PO2 sensor is performed in standard catheters mechanically or by laser. Clinical evaluation is performed with respect to catheter insertion, complications, accuracy of oxygen sensor data and fibrin deposition on the catheter surface. The success rate for catheter insertion is 57% for 138 standard and 50% for 74 laser-cut catheters studied. The proportion of catheter failures (blocked or non-reading) is 14% in laser-cut compared with 30% in standard. These differences are not statistically significant at the 5% level. There is no clinically significant difference in sensor accuracy, with 37.5% of results within +/- 0.05 kPa and 80% within +/- 2.0 kPa of simultaneous blood gas values. Drift is within +/- 0.3 kPa h-1 for 78% of monitoring time. Significant errors of recalibration occur in 6% of calibrations. Scanning electron micrographs demonstrate a much smaller sampling lumen in the laser-cut group, but no reduction in fibrin deposition at the site of the sampling hole. The low success rate for catheter insertion is a problem because of cost implications. The accuracy of the system is usually sufficient for clinical purposes, provided the calibration is checked every 4 h.