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# Inter-laboratory test for gas concentrations measurements of the R3C network's calorimetric chambers

Christophe Montaurier, Patrick Even, C. Couet, Serge Dubois

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Christophe Montaurier, Patrick Even, C. Couet, Serge Dubois. Inter-laboratory test for gas concentrations measurements of the R3C network's calorimetric chambers. Recent Advances and Controversies in the Measurement of Energy Metabolism (RACMEM 2011), Nov 2011, Maastricht, Netherlands. 2011. [hal-01601684](https://hal.science/hal-01601684)

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https://hal.science/hal-01601684

Submitted on 3 Jun 2020

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# Inter-laboratory test for gas concentration measurements of the R3C network's calorimetric chambers.

C. Montaurier¹, P. Even², C. Couet³ and S. Dubois⁴.

¹INRA UMR 1019 UNH-MLE, Clermont Ferrand, ²INRA/INAP-PG UMR 914, Paris, ³Hôpital Bretonneau, Tours, ⁴INRA UMR SENAH, Saint Gilles, France

**Introduction** : Four sites (Clermont Ferrand, Paris, Rennes, and Tours) involved in the R3C (Réseau de Compétence en Chambre Calorimétrique) network have facilities to determine energy expenditure (EE) by indirect calorimetry. EE is computed from the measurements of the O2 and CO2 concentration changes in calorimetric chamber (CC) during the stay of a volunteer or an animal (depending on the site). To obtain reliable values, gas analyzers have to be calibrated using standard gases. As the precision we need for these gases is not available in the gas trade, each site built its own standard gas and control it with its previous standard. Then the values of the standard gases may progressively drift for each site. Moreover such a drift could impact on EE calculation.

The **objective** was to obtain from each site the measurements of the O2 and CO2 concentrations in the same gases mixtures and to examine the degree of concordance/discordance between the four sites and their consequences on EE calculations. This represents a necessary control before multicentric studies involving EE measurements could be carried out.

**Design of the study** : Each site is equipped with a couple of analyzers (O2 and CO2). 2 cylinders (C1 and C2) were filled with 2 different mixtures of gas to obtain appreciative concentrations about 20.200 % and 20.600 % (O2), and 0.800 % and 0.400 % (CO2), respectively for C1 and C2. Both cylinders moved from one site to another. From 5 non-consecutive measurements on each site, we obtain the real mean values for O2 and CO2 concentrations of C1, and the same for C2.

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## Results

<figure><img src="image_4.png" /><figcaption>Figure 1</figcaption></figure>

Fig 1 presents the results obtained for O2. Compared to the mean values, the differences ranged from 0.2 to 4.4% for C1 and from 0.2 to 2.7% for C2. The SD was 3.2 and 2.0% for C1 and C2 respectively.

<figure><img src="image_5.png" /><figcaption>Figure 2</figcaption></figure>

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Fig 2 presents the results obtained for CO2. Compared to the mean values the differences ranged from 0.6 to 2.6% for C1 and from 0.1 to 3.9% for C2 with a SD of 2.2 and 2.8% for C1 and C2 respectively.

<figure><img src="image_7.png" /><figcaption>Figure 3</figcaption></figure>

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The results obtained for the respiratory quotient (RQ) are shown in Fig 3. The differences between sites were 0.016 ± 0.040 for C1 and 0.018 ± 0.051 for C2 respectively.

**Example of consequences on EE**

$$ \text{If drift} = 2\% (\text{O2 and CO2}) $$

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Error on EE is about 1.6 %

**Conclusions** : The results underscore that differences of measurement exist between the 4 sites of the R3C network involved in this test. From this inter-laboratory test first approach, we can quantify differences of O2 and CO2 concentration measurements between the sites. We can take these differences into account, even if they are low, in order to manage multi-sites and epidemiologic studies providing comparable results of EE, after correction if necessary. The setting of correcting methods and the writing of a rigorous inter-laboratory test procedure, are the next steps of this work.