Lack of agreement between tonometric and gastric juice partial carbon dioxide tension

Our goal was to compare measurement of tonometered saline and gastric juice partial carbon dioxide tension (PCO2). In this prospective observational s tudy, 112 pairs of measurements were simultaneously obtained under various hemodynamic conditions, in 15 critical care patients. Linear regression ana lysis showed a significant correlation between the two methods of measuring PCO2 (r(2) = 0.43; P < 0.0001). However, gastric juice PCO2 was systematic ally higher (mean difference 51 mmHg). The 95% limits of agreement were 315 mmHg and the dispersion increased as the values of PCO2 increased. Tonomet ric and gastric juice PCO2 cannot be used interchangeably. Gastric juice PC O2 measurement should be interpreted with caution.