Abstract
Purpose
This study describes methods to improve resting energy expenditure (REE) estimated by the indirect calorimetry by evaluating predictors for the achievement of steady-state conditions (SSC).
Methods
Cross-sectional study carried out with 20 women (30.2 ± 4.1 years; 27.8 ± 6.7 kg/m2). Indirect calorimetry was performed with the Quark RMR® calorimeter, during a 15-min period. VO2 consumption and VCO2 production were measured and data was collected every 5 s. Specific spreadsheet was used to compute the values of Steady REE and Software REE (deltaREE). Bias and concordance between values were assessed by the Bland-Altman plot and Lin’s correlation coefficient.
Results
There is an almost perfect concordance between Software REE and Steady REE (p = 0.001). Steady% was important for predicting deltaREE while variation of carbon dioxide exhaled (CVFECO2) was significant to predict Steady%. Also, CVFECO2 was strongly and significantly correlated with the CV of VO2 (r = 0.83, p = 0001) and with the CV of VCO2 (r = 0.9, p = 0001).
Conclusion
FECO2 should be sustained without huge variations to ensure SSC when using a calorimeter based on the canopy dilution technique with spontaneous breathing patients of similar characteristics. Also, these results suggest that since SSC occurs at least one time in the test, the Software REE may be considered reliable.
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Data availability
Raw data are available upon request from the corresponding author.
Abbreviations
- BLUPs:
-
best linear unbiased predictions
- BMI:
-
body mass index
- CVs:
-
coefficients of variation
- CVFECO2 :
-
variation of carbon dioxide exhaled
- FIO2 :
-
concentrations of oxygen inhaled
- FICO2 :
-
concentrations of carbon dioxide inhaled
- FEO2 :
-
concentrations of oxygen exhaled
- FECO2 :
-
concentrations of carbon dioxide exhaled
- IC:
-
indirect calorimetry
- REE:
-
resting energy expenditure
- SSC:
-
Steady-state conditions
- VCO2 :
-
amount (volume) of carbon dioxide released
- VO2 :
-
amount (volume) of oxygen used
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Acknowledgments
Special thanks go to Neusa Aparecida Brasão Santos Carlos and Maria do Rosário Del Lama de Unamuno for all technical support and to Claire Helen Wardle Munhoz for checking the spelling of the text.
Funding
This study was supported by São Paulo Research Foundation (FAPESP) grants #2010/19821-6, #2012/03485-2, #2012/21579-4, and #2012/21626-2 and National Council for Scientific and Technological Development (CNPq) grant #306824/2006-0 and grant #425775/2016-0 Universal 01/2016.
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JHS, CMML, LWA, and JSM designed the research; JHS and CCML conducted the research; JHS, CFN, CFB, and KP analyzed data and wrote the initial draft of the manuscript; JHS had primary responsibility for final content. All authors contributed towards, and read and approved the final manuscript.
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The research was conducted according to the Helsinki declaration, and the University’s ethical review board approved the study.
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Supplementary information
Supplementary file 1
In this spreadsheet, each row starting at row 14, in columns A to F (in yellow), represents one of the five second measurements of the values of VO2, VCO2, VE, FEO2 and FECO2 recorded. Still starting at row 14, columns G to O (in gray) computed the means of each 5-min interval (i.e., between 5 min and 1 s to 10 min and 1 s; 5 min and 6 s to 10 min and 6 s and so forth). In row 9, from columns A to G (in blue), mean values of VO2, VCO2, Steady REE, RQ, FEO2, FECO2 and VE, obtained from the 60 possible intervals that are compatible with the SSC (SSC intervals), were computed. The columns H up to L, at row 9, showed the percentage of SSC intervals (Steady%) and if all Rest Phase were compatible with SSC’s definition. Row 6, columns N and O (in green) computed the CVs of VO2 and VCO2 from all the Rest Phase. Similarly, row 9, columns M to P, showed the mean values of VO2, VCO2, Software REE and coefficient of variation of the FECO2 (CVFECO2) from all the Rest Phase. Finally, in each test with at least one SSC interval, a deltaREE was calculated as the difference between Steady REE and Software REE. (PNG 979 kb)
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Silvah, J.H., de Lima, C.M.M., Brandão, C.F. et al. Indirect calorimetry: best results with close monitoring of the carbon dioxide fraction in exhaled air. Nutrire 45, 26 (2020). https://doi.org/10.1186/s41110-020-00129-x
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DOI: https://doi.org/10.1186/s41110-020-00129-x