A comparison of resting metabolic rate measurement in adults, using a ventilated canopy or a mixing‐chamber system with a silicone mask

The most common method for measuring resting metabolic rate (RMR) via indirect calorimetry (IC) is using a ventilated canopy system (canopy). Yet, many use a facemask (mask). The purpose of this study was to compare RMR using a canopy and a mask. RMR was measured in 26 participants using a canopy or a mask, followed immediately by the opposite mode in a randomized fashion. RMR was compared between the canopy and mask in males and females using a 2 × 2 repeated‐measures ANOVA. Agreement between the 2 modes and typical error of measurement (TEM) were calculated. Data are mean ± SD. Resting VO 2 and RER were significantly different (VO 2 = 3.72 ± 0.70 vs. 3.46 ± 0.56 mL/kg/min; RER = 0.75 ± 0.04 vs. 0.80 ± 0.04 in canopy vs. mask, p < 0.05). RMR was lower using the mask (1719.71 ± 377.43 vs. 1791.23 ± 387.61 kcal/day, p = 0.026). Mask and canopy RMR showed poor agreement (95% Limit of agreement = −363.5 to 220.5 kcal/day). TEM was larger than the bias between the 2 methods (105.33 kcal/day), which suggests significant random error. Males ( n = 14) had a larger and females ( n = 12) smaller difference in RMR between canopy and mask (−79.14 ± 164.27, p = 0.063, vs. −62.62 ± 135.160 kcal/day, p = 0.166, respectively). We conclude that non‐ventilated facemask cannot produce comparable metabolic data and should not be used for RMR in place of a ventilated canopy.