title: Metabolic monitoring in the intensive care unit: a comparison of the Medgraphics Ultima, Deltatrac II, and Douglas bag collection methods.
abstract: BACKGROUND
  The accuracy of oxygen consumption measurement by indirect calorimeters is poorly validated in mechanically ventilated intensive care patients where multiple confounders exist. This study sought to compare the Medgraphics Ultima (MGU) and Deltatrac II (DTII) devices, and the Douglas bag (DB) technique in mechanically ventilated patients at rest.
  
  
  METHODS
  Prospective comparison of oxygen consumption measurement using three indirect calorimetry techniques in stable, resting mechanically ventilated patients at rest. Oxygen consumption (VO2), carbon dioxide production (VCO2), resting energy expenditure (REE), and respiratory quotient (RQ) were recorded breath-by-breath by the MGU over a 30-75 min period. During this time, simultaneous measurements were taken using the DTII, the DB, or both.
  
  
  RESULTS
  While there was no systematic error (bias) between measurements made by the three techniques (VO2: MGU vs DTII 3.6%, MGU vs DB 3.3%), the limits of agreement were wide (VO2: MGU vs DTII 33%, MGU vs DB 54%).
  
  
  CONCLUSIONS
  Resting oxygen consumption values in stable mechanically ventilated patients measured by the three techniques showed acceptable bias but poor precision. There is an important clinical and research need to develop new indirect calorimeters specifically tailored to measure oxygen consumption during mechanical ventilation.
authors.affiliation: Bloomsbury Institute of Intensive Care Medicine, Division of Medicine, University College London, Cruciform Building, Gower Street, London WC1E 6BT, UK Therapies and Rehabilitation, University College Hospital, London, UK claire.black.09@ucl.ac.uk.
authors.forename: C
authors.initials: C
authors.lastname: Black
authors.affiliation: Integrative Physiology and Critical Illness Group, Faculty of Medicine, University of Southampton, Southampton, UK Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK.
authors.forename: M P W
authors.initials: MP
authors.lastname: Grocott
authors.affiliation: Bloomsbury Institute of Intensive Care Medicine, Division of Medicine, University College London, Cruciform Building, Gower Street, London WC1E 6BT, UK.
authors.forename: M
authors.initials: M
authors.lastname: Singer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002153:Calorimetry, Indirect / Q000295:instrumentation* / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism; D003422:Critical Care / Q000379:methods*; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008660:Metabolism / Q000502:physiology*; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology; D012121:Respiration, Artificial
chemical_list: D002245:Carbon Dioxide
keywords: indirect calorimetry; mechanical; oxygen consumption; validation studies; ventilators