• Basset, Fabien
• Alkanani, Thamir
• Kelly, Liam P.
• Atkinson, Matthew
• Ismail, Mohammad
• Alsubheen, Sanaa A.

Abstract

<jats:sec><jats:title>Objective</jats:title><jats:p>Indirect calorimetry (IC) systems measure the fractions of expired carbon dioxide (F<jats:sub>e</jats:sub>CO<jats:sub>2</jats:sub>), and oxygen (F<jats:sub>e</jats:sub>O<jats:sub>2</jats:sub>) recorded at the mouth to estimate whole-body energy production. The fundamental principle of IC relates to the catabolism of high-energy substrates such as carbohydrates and lipids to meet the body’s energy needs through the oxidative process, which are reflected in the measured oxygen uptake rates (V̇O<jats:sub>2</jats:sub>) and carbon dioxide production rates (V̇CO<jats:sub>2</jats:sub>). Accordingly, it is important to know the accuracy and validity of V̇O<jats:sub>2</jats:sub>and V̇CO<jats:sub>2</jats:sub> measurements when estimating energy production and substrate partitioning for research and clinical purposes. Although several techniques are readily available to assess the accuracy of IC systems at a single point for V̇CO<jats:sub>2</jats:sub> and V̇O<jats:sub>2</jats:sub>, the validity of such procedures is limited when used in testing protocols that incorporate a wide range of energy production (<jats:italic>e.g.</jats:italic>, basal metabolic rate and maximal exercise testing). Accordingly, we built an apparatus that allowed us to manipulate propane burn rates in such a way as to assess the linearity of IC systems. This technical report aimed to assess the accuracy and linearity of three IC systems using our in-house built validation procedure.</jats:p></jats:sec><jats:sec><jats:title>Approach</jats:title><jats:p>A series of trials at different propane burn rates (PBR) (<jats:italic>i.e.</jats:italic>, 200, 300, 400, 500, and 600 mL min<jats:sup>−1</jats:sup>) were run on three IC systems: Sable, Moxus, and Oxycon Pro. The experimental values for V̇O<jats:sub>2</jats:sub> and V̇CO<jats:sub>2</jats:sub> measured on the three IC systems were compared to theoretical stoichiometry values.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>A linear relationship was observed between increasing PBR and measured values for V̇O<jats:sub>2</jats:sub>and V̇CO<jats:sub>2</jats:sub> (99.6%, 99.2%, 94.8% for the Sable, Moxus, and Jaeger IC systems, respectively). In terms of system error, the Jaeger system had significantly (<jats:italic>p</jats:italic> &lt; 0.001) greater V̇O<jats:sub>2</jats:sub>(mean difference (<jats:italic>M)</jats:italic> = −0.057, standard error (<jats:italic>SE)</jats:italic> = 0.004), and V̇CO<jats:sub>2</jats:sub>(<jats:italic>M</jats:italic> = −0.048, <jats:italic>SE</jats:italic> = 0.002) error compared to either the Sable (V̇O<jats:sub>2</jats:sub>, <jats:italic>M</jats:italic> = 0.044, <jats:italic>SE</jats:italic> = 0.004; V̇CO<jats:sub>2</jats:sub>, <jats:italic>M</jats:italic> = 0.024, <jats:italic>SE</jats:italic> = 0.002) or the Moxus (V̇O2, <jats:italic>M</jats:italic> = 0.046, <jats:italic>SE</jats:italic> = 0.004; V̇CO<jats:sub>2</jats:sub>, <jats:italic>M</jats:italic> = 0.025, <jats:italic>SE</jats:italic> = 0.002) IC systems. There were no significant differences between the Sable or Moxus IC systems.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>The multiple PBR approach permitted the assessment of linearity of IC systems in addition to determining the accuracy of fractions of expired gases.</jats:p></jats:sec>

Topics

• impedance spectroscopy
• Carbon
• Oxygen
• size-exclusion chromatography
• calorimetry
• ion chromatography