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

Objective To measure gastric emptying in ventilated critically ill patients 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 μL 13C-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 13CO2 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 13CO2 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 13C-octanoic acid breath test is a novel and useful bedside technique to measure gastric emptying in these patients.