Measuring Resting Energy Expenditure During Extracorporeal Membrane Oxygenation: Preliminary Clinical Experience with a Proposed Theoretical Model

Background: Extracorporeal membrane oxygenation (ECMO) is increasingly used in patients with severe respiratory failure. Indirect calorimetry (IC) is a safe and non-invasive method for measuring resting energy expenditure (REE). No data exist on the use of IC in ECMO-treated patients as oxygen uptake and carbon dioxide elimination are divided between mechanical ventilation and the artificial lung. We report our preliminary clinical experience with a theoretical model that derives REE from IC measurements obtained separately on the ventilator and on the artificial lung.

Methods: A patient undergoing veno-venous ECMO for acute respiratory failure due to bilateral pneumonia was studied. The calorimeter was first connected to the ventilator and oxygen consumption (VO2 ) and carbon dioxide transport (VCO2 ) were measured until steady state was reached. Subsequently, the IC was connected to the membrane oxygenator and similar gas analysis was performed. VO2 and VCO2 values at the native and artificial lung were summed and incorporated in the Weir equation to obtain a REEcomposite .

Results: At the ventilator level, VO2 and VCO2 were 29.5 ml/min and 16 ml/min. VO2 and VCO2 at the artificial lung level were 213 ml/min and 187 ml/min. Based on these values, a REEcomposite of 1703 kcal/day was obtained. The Faisy-Fagon and Harris-Benedict equations calculated a REE of 1373 and 1563 kcal/day.

Conclusion: We present IC-acquired gas analysis in ECMO patients. We propose to insert individually obtained IC measurements at the native and the artificial lung in the Weir equation for retrieving a measured REEcomposite .