Determining the Accuracy and Reliability of Indirect Calorimeters Utilizing the Methanol Combustion Technique

Sepideh Kaviani, Dale A. Schoeller, Eric Ravussin, Edward L. Melanson, Sarah T. Henes, Lara R. Dugas, Ronald E. Dechert, George Mitri, Paul F. M. Schoffelen, Pim Gubbels, Asa Tornberg, Stephen Garland, Marco Akkermans, Jamie A. Cooper*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

BackgroundSeveral indirect calorimetry (IC) instruments are commercially available, but comparative validity and reliability data are lacking. Existing data are limited by inconsistencies in protocols, subject characteristics, or single-instrument validation comparisons. The aim of this study was to compare accuracy and reliability of metabolic carts using methanol combustion as the cross-laboratory criterion.

MethodsEight 20-minute methanol burn trials were completed on 12 metabolic carts. Respiratory exchange ratio (RER) and percent O-2 and CO2 recovery were calculated.

ResultsFor accuracy, 1 Omnical, Cosmed Quark CPET (Cosmed), and both Parvos (Parvo Medics trueOne 2400) measured all 3 variables within 2% of the true value; both DeltaTracs and the Vmax Encore System (Vmax) showed similar accuracy in measuring 1 or 2, but not all, variables. For reliability, 8 instruments were shown to be reliable, with the 2 Omnicals ranking best (coefficient of variation [CV] <1.26%). Both Cosmeds, Parvos, DeltaTracs, 1 Jaeger Oxycon Pro (Oxycon), Max-II Metabolic Systems (Max-II), and Vmax were reliable for at least 1 variable (CV 3%). For multiple regression, humidity and amount of combusted methanol were significant predictors of RER (R-2 = 0.33, P <.001). Temperature and amount of burned methanol were significant predictors of O-2 recovery (R-2 = 0.18, P <.001); only humidity was a predictor for CO2 recovery (R-2 = 0.15, P <.001).

ConclusionsOmnical, Parvo, Cosmed, and DeltaTrac had greater accuracy and reliability. The small number of instruments tested and expected differences in gas calibration variability limits the generalizability of conclusions. Finally, humidity and temperature could be modified in the laboratory to optimize IC conditions.

Original languageEnglish
Pages (from-to)206-216
Number of pages11
JournalNutrition in Clinical Practice
Volume33
Issue number2
DOIs
Publication statusPublished - Apr 2018

Keywords

  • metabolic cart
  • reliability
  • accuracy
  • indirect calorimetry
  • methanol
  • energy metabolism
  • DAILY ENERGY-EXPENDITURE
  • RESTING METABOLIC-RATE
  • GAS-EXCHANGE MEASUREMENTS
  • HIGH-FAT DIET
  • ANALYSIS SYSTEMS
  • MIXING CHAMBER
  • WEIGHT-GAIN
  • VALIDITY
  • EXERCISE
  • VALIDATION

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