Indirect Calorimetry Estimation Research Articles

Development and Evaluation of an Activity Measure for People with Spinal Cord Injury

To develop and conduct a preliminary assessment of the content validity, test-retest reliability, and convergent validity of the Physical Activity Recall Assessment for People with Spinal Cord Injury (PARA-SCI), a new physical activity measure for people with SCI. The scale format, interview guidelines, and activity intensity classification system were developed and content validated using qualitative and quantitative methodologies in multiple samples of people with SCI and their caregivers. Test-retest reliability (1-wk interval) was examined by administering the PARA-SCI via telephone to 102 men and women with SCI. Convergent validity was examined by assessing relationships between PARA-SCI scores and activity levels as determined by indirect calorimetry (N = 14). In the reliability study, intraclass correlations ranged from 0.45 to 0.91 for the various PARA-SCI activity categories and intensities. In the validity study, correlations between PARA-SCI scores and indirect calorimetry estimates of activity ranged from 0.27 to 0.88. The PARA-SCI shows promise as a measure of physical activity for people with SCI. Further validation research is encouraged using broader samples and alternative validation techniques.

The performance of a variable-flow indirect calorimeter

Indirect calorimetry estimates energy expenditure from measurement of respiratory gas exchange volumes. This paper considers the design and evaluation of an indirect calorimeter, the Europa GEM, suitable for use in nutritional research. The calorimeter is of the ventilated hood, flow-through type and is intended for use with spontaneously breathing patients. Our aim was to develop an accurate, flexible instrument with a high level of automation. Performance was assessed in a laboratory simulation using reference gas injections (n = 24) producing a mean error of in oxygen consumption (), in carbon dioxide production () and in respiratory quotient (RQ). In order to investigate the effect of on error multiplication a further subdivision (n = 8) of tests at , 0.75% and 1% was made by modulating the air flow through the hood. However, the predicted increase in system accuracy with increasing was not apparent in practice. Keywords: indirect calorimetry, metabolism, nutrition, gas exchange

How valid are isotopic measurements of fatty acid oxidation?

These studies were performed 1) to compare two isotopic methods (3H2O and 14CO2 production) of measuring free fatty acid (FFA) oxidation; 2) to determine whether isotopic estimates of fatty acid oxidation during hypoinsulinemia are plausible when compared with those obtained using indirect calorimetry; and 3) to examine whether the delay between the exit of [14C]FFA from plasma and the appearance of 14CO2 in breath is accounted for solely by bicarbonate kinetics. Studies in 11 healthy volunteers revealed that [14C]- and [3H]FFA tracers provide similar estimates of FFA turnover and oxidation. Isotopic estimates of fatty acid oxidation were less than those of indirect calorimetry under basal conditions but equaled or exceeded indirect calorimetry estimates after 3 h of acute hypoinsulinemia (somatostatin induced). After stopping tracer infusions, the half-life of plasma [14C]FFA was 3.7 +/- 0.1 min. The half-life of 14CO2 decay from [14C]bicarbonate was 37 +/- 1 min, and the half-life of 14CO2 decay after discontinuation of [14C]FFA infusion was 141 +/- 10 min. Intracellular preoxidative fatty acid pools (possibly triglycerides) most probably account for the marked delay between the exit of FFA tracers from plasma and the appearance of isotopic markers of oxidation in measurable spaces. This delay can result in erroneous estimates of "FFA oxidation." We conclude that tracer measurements of FFA oxidation are invalid under most circumstances.

Validation of the Doubly Labeled Water Technique in Small Insectivorous Bats by Comparison with Indirect Calorimetry

The doubly labeled water technique (DLW) for the measurement of free-living energy expenditure was validated by comparison with indirect calorimetry for nine small (<10 g) insectivorous bats (n = 7, Pipistrellus pipistrellus; n = 2, Plecotus auritus) over a fivefold range of daily metabolism. The DLW estimates were consistently greater than the indirect calorimetry estimates. The mean algebraic difference was +9.5% with the Lifson and McClintock equation, +5.1% with the Coward et al. equation, and +3.4% with the Schoeller et al. equation. These differences were not significant since the range of errors was large. Mean absolute deviation was 13.5%, 13.7%, and 14.5% for the three respective equations. The assumption of a constant respiratory quotient (RQ) did not introduce significant error. The overestimate of energy expenditure made by the DLW technique is consistent with previous validation studies on mammals. One potential source of this error is that the fractional turnover of the oxygen label includes...