Non-invasive Measurements of Energy Expenditure and Respiratory Quotient by Respiratory Mass Spectrometry in Children on Extracorporeal Membrane Oxygenation-A Pilot Study

Extracorporeal membrane oxygenation (ECMO) provides temporary life-saving support for pediatric patients with severe cardiac failure, but causes metabolic disturbances and altered nutritional requirements. However, few studies have addressed the optimal energy supply to meet the demand of these children, largely due to technical difficulties with their invasive nature. We have adapted respiratory mass spectrometry to continuously measure O-2 consumption and CO2 production in the gas exchange across the ECMO oxygenator, as well as that across the ventilator. This study aimed to assess energy expenditure (EE) and respiratory quotient (RQ) in children on ECMO. Five children (aged 0.3 to 36 months, median 20) were studied between Day 1 and Day 6 on ECMO. EE and RQ were measured in sequential fashion at the child's native lungs and ECMO oxygenator using respiratory mass spectrometry. Measurements were collected at 4-h intervals, with the means in 24h representing the values of each day. Each child's caloric and protein intakes were recorded for each day. Between ECMO Days 1 and 6, there was a small but significant increase in EE from 40 to 46kcal/kg/day (P=0.03). In comparison, the caloric intake significantly increased by twice as much as EE from 30 to 61kcal/kg/day (P=0.017). As a result, RQ significantly increased from 0.6 to 1.0 (P<0.0001). Protein intake significantly increased during ECMO Days 1 to 6 from 0.5 to 1.5g/kg/day (P=0.04). Respiratory mass spectrometry is feasible to provide a unique and safe technique to measure EE and RQ in patients on ECMO. Without this knowledge, inadequate feeding may occur. Further studies are warranted in a larger patient population to provide better information to guide clinical practice in this special group of critically ill children.