Accuracy and performance of a modified continuous intravascular blood gas monitoring device during thoracoscopic surgery

Objective: The only commercially available continuous intravascular blood gas monitoring system for adults, the Paratrend (Diametrics Medical Inc, High Wycombe, UK), was modified by the manufacturer to the Paratrend 7+ (PT7+) in 1999. The aim of this study was to evaluate the modified probe over a wide range of blood gas and pH values during thoracoscopic surgery in a similar setup as done with the previous model. Design: Prospective methods comparison study. Setting: University hospital. Participants: Twenty-three patients. Interventions: Elective thoracoscopic surgery. Measurements and Main Results: One hundred thirteen PT7+ readings and their corresponding arterial blood gas and pH measurements (ABGA) were evaluated. The ranges for ABGA values were 50 to 474 mmHg for PO2, 29 to 58 mmHg for PCO2, and 7.28 to 7.49 for pH. Bland and Altman analysis revealed a bias +/- 2 standard deviation of -20 +/- 86 mmHg for PO2, 3 9 mmHg for PCO2, and -0.01 +/- 0.06 for pH. No specific complications attributable to the probe were observed. Conclusion: In patients undergoing thoracoscopic surgery with rapidly changing blood gas parameters, the PT7+ device is a valuable trend indicator and hence may be helpful for clinical decision making. However, the underestimation of PO2 values by 20 mmHg on average and the wide limits of agreement documented in this study must be regarded as limiting factors. (C) 2004 Elsevier Inc. All rights reserved.