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Assessing Validity and Reliability of Resting Metabolic Rate in Six Gas Analysis Systems

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Abstract

The Deltatrac Metabolic Monitor (DTC) (VIASYS Healthcare Inc, SensorMedics, Yorba Linda, CA), one of the most popular indirect calorimetry systems for measuring resting metabolic rate (RMR) in human subjects, is no longer being manufactured. This study compared five different gas analysis systems to the DTC. RMR was measured by the DTC and at least one other instrument at three study sites for a total of 38 participants. The five indirect calorimetry systems included the MedGraphics CPX Ultima (Medical Graphics Corp, St Paul, MN), the MedGem (Microlife USA, Golden, CO), Vmax Encore 29 System (VIASYS Healthcare Inc, Yorba Linda, CA), the TrueOne 2400 (Parvo Medics, Sandy, UT), and the Korr ReeVue (Korr Medical Technologies, Salt Lake City, UT). Validity was assessed using paired t tests to compare means; reliability was assessed by using both paired t tests and root mean square calculations with F tests for significance. Within-subject comparisons for validity of RMR revealed a significant difference between the DTC and the Ultima system. Bland-Altman plot analysis showed significant bias with increasing RMR values for the Korr and MedGem systems. Respiratory exchange ratio (RER) analysis showed a significant difference between the DTC and the Ultima system and a trend for a difference with the Vmax system (P=0.09). Reliability assessment for RMR revealed that all instruments had a significantly larger coefficient of variation (CV) (ranging from 4.8% to 10.9%) for RMR compared to the 3.0% CV for the DTC. Reliability assessment for RER data showed none of the instrument CVs was significantly larger than the DTC CV. The results were quite disappointing because none of the instruments equaled the within-person reliability of the DTC. The TrueOne and Vmax systems were the most valid instruments in comparison with the DTC for both RMR and RER assessment. Further testing is needed to identify an instrument with the reliability and validity of the DTC.

Section snippets

Subjects

Five men and seven women, all healthy, with an average age of 24±11 years and body mass index (BMI) of 21.8±2.1 were recruited from the University of Wisconsin–Madison through on-campus advertising to participate in a 2-day RMR study. The study was approved by the Institutional Review Board of the University of Wisconsin–Madison and informed written consent was obtained. Exclusion criteria included a history of metabolic or pulmonary disease, implanted electrical devices, and claustrophobia.

Internal Validity and Reliability of the DTC

Alcohol burn tests performed at the University of Wisconsin–Madision and Loyola University Medical Center tested the accuracy of the DTC. At the University of Wisconsin–Madison, burns revealed carbon dioxide at 98.9%±1.2% of theoretical and oxygen at 98.9%±1.1% of theoretical. Loyola University Medical Center burns yielded 101.9%±2.1% and 100.3%±0.9% of theoretical for carbon dioxide and oxygen, respectively. Correction factors developed based on these data were applied to DTC data from the

Conclusions

Because the DTC instrument is no longer being manufactured, another valid and reliable gas analysis system is needed. We compared five systems with the DTC and found that the TrueOne and the Vmax were the most valid gas analysis systems of those tested for measuring both RMR and RER relative to the DTC; however, none of the gas analysis systems tested can be considered adequately reliable for use in a research setting, although the TrueOne comes close. This is disappointing considering that the

J. A. Cooper is a graduate student, Department of Nutritional Sciences, University of Wisconsin–Madison, Madison, WI

References (10)

  • S. Blanc et al.

    Energy requirements in the eighth decade of life

    Am J Clin Nutr

    (2004)
  • M.P. St Onge et al.

    A new hand-held indirect calorimeter to measure postprandial energy expenditure

    Obes Res

    (2004)
  • D.S. Alam et al.

    Validity and reproducibility of resting metabolic rate measurements in rural Bangladeshi women: Comparison of measurements obtained by Medgem and by Deltatrac device

    Eur J Clin Nutr

    (2005)
  • J.B. Weir

    New methods for calculating metabolic rate with special reference to protein metabolism

    J Physiol

    (1949)
  • J.R. Dobratz et al.

    Comparison of handheld to metabolic cart indirect calorimetry for resting energy expenditure assessment in extremely obese women

    Top Clin Nutr

    (2007)
There are more references available in the full text version of this article.

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J. A. Cooper is a graduate student, Department of Nutritional Sciences, University of Wisconsin–Madison, Madison, WI

A. C. Watras is a research coordinator, Department of Nutritional Sciences, University of Wisconsin–Madison, Madison, WI

D. A. Schoeller is a professor, Department of Nutritional Sciences, University of Wisconsin–Madison, Madison, WI

M. J. O'Brien is pulmonary function lab manager, Pulmonary Lab, University of Wisconsin Hospital and Clinics, Madison, WI

A. Luke is an associate professor, Department of Preventive Medicine and Epidemiology, Loyola University, Maywood, IL

J. R. Dobratz is a graduate student, Department of Food Science and Nutrition, University of Minnesota, St Paul

C. P. Earthman is an assistant professor, Department of Food Science and Nutrition, University of Minnesota, St Paul

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