Delayed gastric emptying in ventilated critically ill patients:: Measurement by 13C-octanoic acid breath test

Objective: To measure gastric emptying in ventilated critically ill patents with a new noninvasive breath test. Design: Single-center, open study. Setting: Combined medical and surgical intensive care unit of a university hospital. Subjects: Thirty unselected mechanically ventilated critically ill patients receiving gastric feeding and 22 healthy volunteers. Interventions: None. Patients: After 4 hrs without feeding, intragastric infusion of 100 mL of a liquid meal (Ensure) labeled with 100 muL C-13-octanoic acid. End-expiratory breath samples were collected into evacuated tubes from the respirator circuit every 5 mins for the first hour, then every 15 mins for 3 hrs. End-expiratory breath samples were also collected from volunteers studied supine after an overnight fast following an identical infusion via a nasogastric tube. Breath (CO2)-C-13 was measured with an isotope ratio mass spectrometer. Measurements and Main Results: Performance of the breath test posed no difficulty or interference with patient care. The CO2 level was >1% in 1297/1300 breath samples, indicating satisfactory end-expiratory timing. Data are median and interquartile range. Gastric emptying was slower in patients compared with volunteers: gastric emptying coefficient 2.93 (2.17-3.39) vs. 3.58 (3.18-3.79), p < .001 and gastric half emptying time, derived from the area under the (CO2)-C-13 curve, 155 min (130-220) vs. 133 min (120-145), p < .008. Fourteen of the 30 patients had a gastric emptying coefficient < 95% of all volunteers and 11 had a gastric half emptying time longer than 95% of all volunteers. The Acute Physiology and Chronic Health Evaluation (APACHE II) score (median 22, range 13-43) either at admission or on the day of the study did not correlate with gastric emptying coefficient. Conclusion: Gastric emptying of a calorie-dense liquid meal is slow in 40% to 45% of unselected mechanically ventilated patients in a combined medical and surgical intensive care unit. The C-13-octanoic acid breath test is a novel and useful bedside technique to measure gastric emptying in these patients.