title: Validation of an indirect calorimeter using n-of-1 methodology.
abstract: BACKGROUND
  Validation data for currently available indirect calorimeters is limited. The purpose of this investigation was to validate a newer indirect calorimeter system (Vmax Encore) against a criterion device (Deltatrac Metabolic Monitor) in spontaneously breathing mode.
  
  
  METHODS
  An n-of-1 methodology was used in which both indirect calorimeters were employed in the same subject repeatedly until 15 measurement pairs were generated for oxygen consumption (VO2), carbon dioxide production (VCO2), resting metabolic rate (RMR), and respiratory quotient (RQ). Bias was defined as a 95% confidence interval of differences between devices that excluded zero. A set of intradevice measurement pairs was also obtained to analyze the precision of the Vmax and Deltatrac (precision defined as not more than 5% of measurements being ≥5% different).
  
  
  RESULTS
  Both Vmax and Deltatrac precisely measured VO2 and RMR. The largest intradevice difference for RMR in the Deltatrac was 4.7% (one of 20 pairs) and in the Vmax 4.8%. On the other hand, VCO2 and RQ were not measured precisely by either device, with 10% or more of the measurement pairs differing by ≥ 5%. The Vmax was biased toward low measurement of VO2 and RMR relative to the Deltatrac. Oxygen consumption was on average 4.5 ± 2.4% lower for the Vmax device compared to Deltatrac while RMR was lower by an average of 4.1 ± 2.2%.
  
  
  CONCLUSIONS
  The Vmax Encore indirect calorimeter is a precise instrument for measuring VO2 and RMR in spontaneously breathing individuals, but it is biased toward lower values compared to the Deltatrac.
authors.affiliation: Department of Clinical Nutrition, Penn State Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, United States; Department of Nursing, Penn State Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, United States. Electronic address: Dfrankenfield@hmc.psu.edu.
authors.forename: David C
authors.initials: DC
authors.lastname: Frankenfield
authors.affiliation: Department of Clinical Nutrition, Penn State Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, United States; Department of Nursing, Penn State Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, United States.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Ashcraft
authors.affiliation: Department of Nursing, Penn State Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, United States.
authors.forename: Carola
authors.initials: C
authors.lastname: Wood
authors.affiliation: Department of Public Health Sciences, Penn State College of Medicine, 500 Hope Drive, Suite 2200, Hershey, PA 17033, United States.
authors.forename: Vernon M
authors.initials: VM
authors.lastname: Chinchilli
mesh_terms: D001481:Basal Metabolism; D015992:Body Mass Index; D001835:Body Weight; D002153:Calorimetry, Indirect / Q000295:instrumentation* / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism; D002149:Energy Intake; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods*; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results; D012119:Respiration
chemical_list: D002245:Carbon Dioxide
keywords: Energy expenditure; Indirect calorimetry; Validation