Table 2.

Overview of comparative studies of IC devices in mechanically ventilated patients [16, 64–67]

	Q-NRG®	Deltatrac®
Deltatrac® (Datex, Finland)	- (No) significant difference in measured REE [16] - Measurements using Q-NRG® significantly faster [16]
QUARK RMR® (Cosmed, Italy)	- Significant difference in measured REE (p = 0.038) - Measurements using Q-NRG® significantly faster [16]	- No significant difference in mean REE (p = 0.166) - No significant differences EE, VCO₂, and VO₂ [66] - Significant difference in RQ (p < 0.0001) not favoring Deltatrac®, due to measurement values outside the physiological range [60] - Overestimation of VO₂ and VCO₂ by QUARK RMR® [67]
Vmax® (Vyaire, USA)	- Significant difference in measured REE (p < 0.001) - Measurements using Q-NRG® significantly faster [16]	- No significant difference in REE (p = 0.8) is not reliable enough in a clinical research setting [65]
E-COVX® (Datex-Ohmeda, Finland)	- No significant difference in measured REE (p = 0.165) - No significant difference in the duration of measurement	- Overestimation of VO₂ and VCO₂ by E-COVX® [67]
CCM Express® (Medgraphics, USA)		- Significant difference in mean REE (p < 0.0001) - Significant difference in RQ (p < 0.0001) - Significant differences in RQ and VO₂ and VCO₂ (p < 0.0001) [66]