AIM: To determine the response of the proximal stomach to small intestinal nutrients in critically iii patients.METHODS: Proximal gastric motility was measured in 13 critically iii patients (49.3 ± 4.7 years) and 12 healthy volunteers (27.7 ± 2.9 years) using a barostat technique.Recordings were performed at baseline, during a 60-min intra-duodenal infusion of Ensure(R) (2 kcal/min), and for 2 h following the infusion. Minimum distending pressure (MDP), intra-bag volume and fundic wave activity were determined.RESULTS: The MDP was higher in patients (11.7 ± 1.1 vs 7.8 ± 0.7 mmHg; P ＜ 0.01). Baseline intrabag volumes were similar in the 2 groups. In healthy subjects, a bimodal proximal gastric volume response was observed. In patients, the initial increase in proximal gastric volume was small and delayed, but eventually reached a maximal volume similar to that of healthy subjects. In healthy subjects, the proximal gastric volume rapidly returned to baseline level after nutrient infusion (median 18 min). In contrast, the recovery of volume to baseline was delayed in critically ill patients (median 106 min). In 6 patients, the volume had not returned to baseline level 2 hours after nutrient infusion.In patients, fundic volume waves were less frequent (P ＜ 0.05) and had lower amplitude (P ＜ 0.001), compared to healthy subjects.CONCLUSION: In critical illness, proximal gastric motor responses to small intestinal nutrient stimulation are abnormal.