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 study, 112 pairs of measurements were simultaneously obtained under various hemodynamic conditions, in 15 critical care patients. Linear regression analysis showed a significant correlation between the two methods of measuring PCO₂ (r ² = 0.43; P < 0.0001). However, gastric juice PCO₂ was systematically higher (mean difference 51 mmHg). The 95% limits of agreement were 315 mmHg and the dispersion increased as the values of PCO₂ increased. Tonometric and gastric juice PCO₂ cannot be used interchangeably. Gastric juice PCO₂ measurement should be interpreted with caution.