title: Gastric emptying measurement of liquid nutrients using the (13)C-octanoate breath test in critically ill patients: a comparison with scintigraphy.
abstract: OBJECTIVE
  Scintigraphy is considered the most accurate technique for the measurement of gastric emptying (GE) but, for patients in the intensive care unit, it is technically demanding, involves radiation and can interfere with care. The (13)C-octanoate breath test ((13)C-OBT) is a simple, non-invasive technique that does not involve radiation exposure.
  
  
  OBJECTIVE
  To evaluate the performance of the (13)C-OBT in the assessment of GE in critically ill patients.
  
  
  METHODS
  The GE was assessed in 33 mechanically ventilated patients (23 M; 54.3 ± 3.0 yrs; APACHE II: 22.0 ± 1.1). Following test meal administration (100 ml Ensure(®)), concurrent scintigraphic measurement and breath samples ((13)C-OBT) were collected over 4 h. Scintigraphic meal retention was determined and the gastric emptying coefficient (GEC) and half emptying time [t50(BT)] were calculated for the (13)C-OBT. Delayed GE was defined as meal retention >13 % at 180 min.
  
  
  RESULTS
  Delayed GE was identified in 27/33 patients. Meal retention correlated modestly with t50(BT) (r = 0.55-0.66; P < 0.001) and well with GEC (r = -0.63 to -0.74; P < 0.0001). The strength of agreement between the two techniques was highest between GEC and retention at 120 min. The best cut-off GEC for defining delayed GE was 3.25 (AUC = 0.75; 95 % CI = 0.52-0.99; P = 0.05), with 89 % sensitivity and 67 % specificity to detect delayed GE. The GE was delayed in all (23/23) patients with feed intolerance (GRV > 250 ml) on scintigraphy and 91 % (21/23) patients on (13)C-OBT.
  
  
  CONCLUSIONS
  In critical illness, there was a correlation between (13)C-OBT and gastric scintigraphy, with GEC performing as a better and more sensitive marker of detecting delayed GE than t50. However the relatively wide 95 % confidence intervals suggest that (13)C-OBT is more suitable as a technique to assess GE in a group setting for research studies rather than for individual patients in clinical practice.
authors.affiliation: Department of Gastroenterology and Hepatology, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia 5000, Australia. quoc.nguyen@health.sa.gov.au
authors.forename: Nam Q
authors.initials: NQ
authors.lastname: Nguyen
authors.forename: Laura K
authors.initials: LK
authors.lastname: Bryant
authors.forename: Carly M
authors.initials: CM
authors.lastname: Burgstad
authors.forename: Marianne
authors.initials: M
authors.lastname: Chapman
authors.forename: Adam
authors.initials: A
authors.lastname: Deane
authors.forename: Max
authors.initials: M
authors.lastname: Bellon
authors.forename: Kylie
authors.initials: K
authors.lastname: Lange
authors.forename: Dylan
authors.initials: D
authors.lastname: Bartholomeuz
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
authors.forename: Richard H
authors.initials: RH
authors.lastname: Holloway
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fraser
mesh_terms: D001944:Breath Tests / Q000379:methods*; D002210:Caprylates; D002247:Carbon Isotopes; D016638:Critical Illness; D004750:Enteral Nutrition; D005260:Female; D005746:Gastric Emptying; D018589:Gastroparesis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D006801:Humans; D007362:Intensive Care Units; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D012121:Respiration, Artificial; D012680:Sensitivity and Specificity
chemical_list: D002210:Caprylates; D002247:Carbon Isotopes; C031492:octanoic acid