title: Delayed gastric emptying in ventilated critically ill patients: measurement by 13 C-octanoic acid breath test.
abstract: OBJECTIVE
  To measure gastric emptying in ventilated critically ill patients with a new noninvasive breath test.
  
  
  METHODS
  Single-center, open study.
  
  
  METHODS
  Combined medical and surgical intensive care unit of a university hospital.
  
  
  METHODS
  Thirty unselected mechanically ventilated critically ill patients receiving gastric feeding and 22 healthy volunteers.
  
  
  METHODS
  None.
  
  
  METHODS
  After 4 hrs without feeding, intragastric infusion of 100 mL of a liquid meal (Ensure) labeled with 100 microL 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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Gastrointestinal Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia.
authors.forename: M A
authors.initials: MA
authors.lastname: Ritz
authors.forename: R
authors.initials: R
authors.lastname: Fraser
authors.forename: N
authors.initials: N
authors.lastname: Edwards
authors.forename: A C
authors.initials: AC
authors.lastname: Di Matteo
authors.forename: M
authors.initials: M
authors.lastname: Chapman
authors.forename: R
authors.initials: R
authors.lastname: Butler
authors.forename: P
authors.initials: P
authors.lastname: Cmielewski
authors.forename: J P
authors.initials: JP
authors.lastname: Tournadre
authors.forename: G
authors.initials: G
authors.lastname: Davidson
authors.forename: J
authors.initials: J
authors.lastname: Dent
mesh_terms: D018806:APACHE; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001944:Breath Tests / Q000379:methods; D002210:Caprylates / Q000378:metabolism*; D002245:Carbon Dioxide / Q000737:chemistry*; D016022:Case-Control Studies; D003422:Critical Care; D004750:Enteral Nutrition; D005260:Female; D005746:Gastric Emptying; D006801:Humans; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial
chemical_list: D002210:Caprylates; D002245:Carbon Dioxide; C031492:octanoic acid