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

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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

To cite this version:

Christophe Montaurier, Patrick Even, C. Couet, Serge Dubois. Inter-laboratory test for gas concentra-tions 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�

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Inter-laboratory test for gas concentration measurements of the

R3C network's calorimetric chambers.

C. Montaurier

1

, P. Even

2

, C. Couet

3

and S. Dubois

4

.

1_{INRA UMR 1019 UNH-MLE, Clermont Ferrand,}2_{INRA/INAP-PG UMR 914, Paris,}3_{Hôpital Bretonneau, Tours,}4_{INRA 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.

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.

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. CO2 C1 C2

O2 Clermont Ferrand CO2 O2 Paris CO2 O2 Rennes CO2 O2 Tours

Results

O2 for Cylinder 1 (C1) 20,120 20,130 20,140 20,150 20,160 20,170 20,180 20,190 20,200 20,210 20,220

Site 1 Site 2 Site 3 Site 4

O 2 ( % ) Mean O2 O2 for Cylinder 2 (C2) 20,570 20,580 20,590 20,600 20,610 20,620 20,630

O 2 ( % ) Mean O2 Figure 1

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.

CO2 for Cylinder 1 (C1)

0,710 0,720 0,730 0,740 0,750 0,760 0,770 0,780 0,790

C O 2 ( % ) Mean CO2

CO2 for Cylinder 2 (C2)

0,330 0,340 0,350 0,360 0,370 0,380 0,390 0,400 0,410

C O 2 ( % ) Mean CO2 Figure 2

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.

Estimated RQ 0,900 0,950 1,000 1,050 1,100 1,150 1,200 1,250 1,300

RQ

C1 C2

Mean RQ C1 Mean RQ C2

Figure 3

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