Impact of enteral feeding on gastric tonometry in healthy volunteers and critically ill patients

Background: Enteral feeding may interfere with gastric tonometry measuremen t. The effect of enteral nutrition on gastric tonometry has not been fully documented. Methods: Seven healthy volunteers and nine stable intensive care unit (ICU) patients with poor tolerance of gastric feeding were investigated. Consecu tive continuous postpyloric and gastric feeding, both at two different rate s (40 and 100 ml.h(-1), respectively), and an intragastric 200 mi nutrition bolus were studied. Gastric intramucosal PCO2 (PiCO(2)) was measured by ai r tonometry and in patients a gastric intramucosal-arterial PCO2 difference (PCO2 gap) was calculated. Hemodynamics and blood gases were also measured . Results: In volunteers, PiCO(2) remained stable during the postpyloric phas e. During continuous gastric feeding PiCO(2) did not change significantly, although in 4 volunteers PiCO(2) increased >0.5 kPa. PiCO(2) decreased sign ificantly after gastric bolus from 6.9 +/-0.4 to 6.1 +/-0.5 kPa (P <0.05). Eight patients had an increased PCO2 gap (>1 kPa) at baseline (1.8 +/-0.6 k Pa), PCO2 gap changes during the whole study were not statistically signifi cant. However, during the postpyloric phase (or immediately afterwards), th e PCO2 gap increased by moro than 0.5 kPa in 5 patients. After gastric bolu s, a decrease in PCO2 gay >0.5 kPa was seen in 5 patients. Conclusion: in volunteers, postpyloric feeding does not interfere with gast ric tonometry measurement and gastric bolus leads to a PiCO(2) decrease. Th e impact of postpyloric and gastric feeding on gastric tonometry in ICU pat ients with compromised gut is variable.