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  • Letter
  • Open Access

VCO2 calorimetry: stop tossing stones, it’s time for building!

  • 1Email author,
  • 1 and
  • 1
Critical Care201620:399

  • Published:

The original article was published in Critical Care 2015 19:370


  • Energy expenditure
  • Nutrition
  • Intensive care unit

We followed with interest the discussion [1, 2] fueled by the study of Stapel et al. [3] 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 [4].

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 [5] 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.




Energy expenditure


Carbon dioxide production



Not applicable.


The authors declare that they have received no external funding.

Availability of data and materials

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Authors’ contributions

EDW designed the paper; EDW, PMH, and HDS participated in drafting the manuscript, and have read and approved the final version.

Authors’ information

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Competing interests

The authors declare that they have no competing interests.

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Authors’ Affiliations

ICU Department, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, 101 Laarbeeklaan, 1090 Brussels, Belgium


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  3. 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.View ArticlePubMedPubMed CentralGoogle Scholar
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© The Author(s). 2016