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VCO2 calorimetry: stop tossing stones, it’s time for building!
Critical Care volume 20, Article number: 399 (2016)
We followed with interest the discussion [1, 2] fueled by the study of Stapel et al.  who reported fairly accurate assessment of energy expenditure (EE) in critically ill patients based on ventilator-derived carbon dioxide production (VCO2). The proposed technique is elegant and valid but has inherent limitations. It is applicable in patients who are in one way or another ventilator-dependent but not in spontaneously breathing yet oxygen-dependent subjects. We concur that VO2 is the most relevant variable for EE measurement. However, the most accurate and precise estimation of EE in a critically ill population can only be obtained by sampling of inspired and expired oxygen/carbon dioxide concentrations and measuring expired gas flow. This is the core task of indirect calorimetry .
Initiative has been undertaken to develop a ‘full option’, easy-to-use, accurate, and affordable indirect calorimeter. The project is supported by the European Society of Intensive Care Medicine and the European Society of Parenteral and Enteral Nutrition  and has actually reached Technology Readiness Level. It is probably only a matter of time before such a device will render all current mathematical uproar obsolete.
- VCO2 :
Carbon dioxide production
Singer P. Simple equations for complex physiology: can we use VCO2 for calculating energy expenditure? Crit Care. 2016;20:72.
Pielmeier U, Andreassen S. VCO2 calorimetry is a convenient method for improved assessment of energy expenditure in the intensive care unit. Crit Care. 2016;20:224.
Stapel SN, de Grooth HJS, Alimohamad H, Elbers PW, Girbes AR, Weijs PJ, et al. Ventilator-derived carbon dioxide production to assess energy expenditure in critically ill patients: proof of concept. Crit Care. 2015;19:370.
Frankenfield DC. On heat, respiration, and calorimetry. Nutrition. 2010;26(10):939–50.
Oshima T, Berger MM, De Waele E, Guttormsen AB, Heidegger CP, Hiesmayr M, et al., A position paper by the ICALIC study group. Indirect calorimetry in nutritional therapy. Clin Nutr. 2016;(16):30142-X.
The authors declare that they have received no external funding.
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EDW designed the paper; EDW, PMH, and HDS participated in drafting the manuscript, and have read and approved the final version.
The authors declare that they have no competing interests.
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See related research by Stapel et al. http://ccforum.biomedcentral.com/articles/10.1186/s13054-015-1087-2
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De Waele, E., Honoré, P.M. & Spapen, H.D. VCO2 calorimetry: stop tossing stones, it’s time for building!. Crit Care 20, 399 (2016). https://doi.org/10.1186/s13054-016-1575-z
- Energy expenditure
- Intensive care unit