Indirect calorimetry in canopy mode in healthy subjects: performances of the Q-NRG device compared to the Deltatrac II

Background: Extensive validation of the Q-NRG indirect calorimeter in canopy mode, especially against reference devices, is lacking. The aim of this study was to test its agreement in canopy mode with the Deltratrac II, which has always been considered as the gold standard indirect calorimeter in daily practice.

Methods: Healthy volunteers underwent indirect calorimetry with two consecutive assessments, using Q-NRG and Deltatrac II, both in canopy mode, in a random order, after careful calibrations. Body position, fasting conditions and environment were standardized. Agreement between the two devices was evaluated by paired Student’s t test, correlation coefficients, and Bland-Altman plots.

Results: Sixty-one adults (85.2% male, aged 25.7±8.4 y, BMI 23.3±2.9 kg/m2) were included. Measured energy expenditure was similar whether it was measured using Q-NRG or Deltatrac II: 1816±361 kcal/day or 1809±260 kcal/day (p=0.803), respectively. There was a significant positive correlation between the two measures (ρ=0.78, p= <0.01). The Q-NRG slightly overestimated the energy expenditure compared to the Deltatrac II measure: the bias ± limits of agreement was 7 ± 227 kcal/day.

Conclusion: In healthy volunteers breathing spontaneously, the Q-NRG in canopy mode performed similarly to the Deltatrac II for energy expenditure measurement. The present study confirms the previously demonstrated accuracy of the Q-NRG device, and supports its clinical use in canopy mode.

Keywords: indirect calorimetry, canopy, energy expenditure, nutrition.