Reliability of, and Agreement Between, two Breath-by-Breath Indirect Calorimeters at Varying Levels of Inspiratory Oxygen

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Background: Indirect calorimetry (IC) is considered the accurate way of measuring energy expenditure (EE). IC devices often apply the Haldane transformation, introducing errors at inspiratory oxygen fraction (FiO 2) >60%. The aim was to assess measurement reliability and agreement between an unevaluated IC (device 2) (Beacon Caresystem, Mermaid Care A/S, Noerresundby, Denmark) not using Haldane transformation and an IC that does (device 1) (Ecovx, GE, Helsinki, Finland) at varying FiO 2. Methods: Twenty healthy male subjects participated, with 16 completing the study (33 ± 9 years, 83.3 ± 16 kg, 1.83 ± 0.08 m). Subjects were mechanically ventilated in pressure support (3cmH 2O; positive end-expiratory pressure: 3cmH 2O) at FiO 2 of 21%, 50%, 85%, and 21% for 15 minutes at each FiO 2. Mean EE, oxygen consumption (VO 2), and CO 2 production (VCO 2) were compared within and between devices across FiO 2 levels. Results: Device 2 showed within-device EE significant differences at 21% vs 50% FiO 2 and device 1 for VCO 2 at 50% vs. 85% FiO 2. For all variables, both devices showed reliable measurements at 21% and 50% FiO 2, but at 85%, FiO 2 bias and limits of agreement increased. Between devices, there were significant differences for EE at both 21% and 85% FiO 2 for VO 2 and for VCO 2 at 85% FiO 2. Conclusion: Both systems measured EE, VO 2, and VCO 2 at 21%–85% FiO 2 reliably but with bias at 85% FiO 2. The devices were in agreement at 21% and 50% FiO 2, but further studies need to confirm accuracy at high FiO 2.

Original languageEnglish
JournalNutrition in Clinical Practice
Issue number5
Pages (from-to)767-774
Number of pages8
Publication statusPublished - Oct 2019


  • bias
  • indirect calorimetry
  • mechanical ventilation
  • reproducibility of results
  • resting energy expenditure


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