Gastric mucosal end-tidal PCO2 difference as a continuous indicator of splanchnic perfusion

Gastric mucosal and arterial blood PCO2 must be known to assess mucosal per fusion by means of gastric tonometry. As end-tidal PCO2 (PECO2' is a functi on of arterial PCO2, the gradient between PECO2' and gastric mucosal PCO2 m ay reflect mucosal perfusion. We studied the agreement between two methods to monitor gut perfusion. We measured the difference between gastric mucosa l PCO2 lair tonometry) and PECO2' (=DPCO2gas) and the difference between ga stric mucosal PCO2 (saline tonometry) and arterial blood P-CO2 (=DPCO2sal) in 20 patients with or without lung injury. DPCO2gas was greater than DPCO2 sal but changes in DPCO2gas reflected changes in DPCO2sal. The bias between DPCO2gas and DPCO2sal was 0.85 kPa and precision 1.25 kPa. The disagreemen t between DPCO2gas and DPCO2sal increased with increasing dead space. We pr opose that the disagreement between the two methods studied may not be clin ically important and that DPCO2gas may be a method for continuous estimatio n of splanchnic perfusion.